US2945097A

US2945097A - Rotary limit switch

Info

Publication number: US2945097A
Application number: US791099A
Authority: US
Inventors: Hake Walter Thomas
Original assignee: American Steel Foundries
Current assignee: American Steel Foundries
Priority date: 1959-02-04
Filing date: 1959-02-04
Publication date: 1960-07-12
Anticipated expiration: 1977-07-12

Description

v w. T. HAKE ROTARY LIMIT swrrcu July 12, 1960 Fiied Feb. 4. 1959 I BY mm; 71W 9/- w m 4\ l@ g\ M." J v 5 .2 W

United States Patent f ROTARY LIMIT SWITCH Filed Feb. 4, 19 59, Set. No. 791,099 8 Claims. (Cl. 200-47) This invention relates to limit switch arrangements and more particularly to rotary type limit switches utilized to determine the limits of travel of a movable member.

It is frequently necessary, particularly on automatically controlled machine tools, to provide electrical switch means for automatically terminating the movement, in either direction, of a movable member. It has been recognized in the past that mounting individual conventional limit switches at the terminal points of movement of a member is excessively expensive. 'For this reason, switches have been developed which step down large movements of a machine tool member to comparatively small movements of a rotary member. The rotary member is generally provided with cams arranged to trip limit switches which are enclosed in the same box as the rotary member. However, the-commercially. available devices of this type are complicated, expensive and are not suflicieutly compact for all applications.

Accordingly, the primary object of the present invention is to provide a rotary type limit switch which is comparatively inexpensive to manufacture and which also requires less space than prior art devices of this type.

Other objects and advantages will become apparent from the'following description and accompanying drawings wherein: I

Figure 1 isa longitudinal sectional view of apreferred embodiment of the invention;

Figure 2 is a transverse section taken at line 2-2 of Figure 1;

Figure 3 is a transverse section taken at line 3-3 of Figure 1; and

Figure 4 is similar to Figure 2 but shows an alternate type of construction.

Referring to the drawings, it is seen that the rotary limit switch arrangement is preferably enclosed in a housing having a removable cover 11 (Figure 2). A pair of opposed limit switches 12 are secured to internal bosses (not shown) in the housing in a conventional manner, as for example, by means of mounting screws 14. The limit switches 12 are conventionally provided with spring loaded contacts 16 which, when depressed, make or break a circuit depending on whether the switch is normally open or normally -closed. Details of the switches 12 are not shown because such switches are conventional and well known to those skilled in the art. A rotary member 18, preferably in the form of a worm wheel, has end projections 20 rotatably mounted in recesses 22 of the housing 10. The worm wheel is provided with threads 24 arranged for engagement by a worm 26 which is keyed or otherwise secured to a shaft 28 for rotation therewith. The shaft 28 may be a drive screw for a movable machine tool member and its rotation will therefore be directly proportional to the movement of the member. It will be understood, however, that, alternately, motion of the movable machine tool member could be transmitted to the rotary member 18 by means Patented July 12, 1960 ice.

of a rack,in which case the member 18 would be the pinion of a rack and pinion combination. The rotary member 18 is provided internally thereof withscrew threads 30 which are engageable with a screw 32 in such a manner that rotary motion of the member 18 is translated into linear motion of the screw 32 in a direction axially of the member 18. Furthermore, the common axis of the screw 32 and rotary member 18 is preferably aligned with the contacts 16 of the limit switches 12.

The screw 32 is provided with axial extensions 34 which, in the preferred embodiment, are nonround, preferably square or rectangular, in cross-section and are arranged to be received in correspondingly shaped'openings 36 in the housing 10. The purpose of this construction is to prevent rotary motion of the member 18 from being transferred to the screw 32. In the embodiments of Figures 2 and 3, the extensions 34 are square in section and received entirely in the housing 10. This construction is preferred because no machining is required in the cover 11. An alternate embodiment is illustrated in Figure 4 wherein the extensions 34 are oval in section and received partially in the housing and partially in the cover. The extensions 34 of the screw 32 may be arranged to directly actuate the contacts 16 of the limit switches 12, but this is only feasible in those instances where it is not intended to frequently vary the stroke of the controlled machine tool member. However, more frequently, some means of adjustment is required and, according to the present invention, such adjustment is acconiplished by means of inserts 38 which are complementary in cross-section to, and slidably received in, the openings 36. The inserts for a particular distanceof travel of the machine tool member may be easily and quickly assembled or replaced merely by removing the cover portion 11 (Figures 2, 3 and 4) of the housing 10 whereupon the entire switch arrangement becomes accessible.

The adjustment inserts 38 may be secured to the extensions 34 in any conventional manner or, alternately, may ride freely in the openings 36. In the latter instance, after .a limit switch has been actuated to terminate the movement of the con-trolled member in a given direction and further when the direction of movement of the member is reversed so that the screw 32 moves away from the associated insert 38, the spring action of the contact means 16 must be sufiicient to move the insert away from the limit switch so that the position of the internal switch contacts may simultaneously be reversed.

Preferably, in order to ensure that the switch action is promptly reversed, a leaf spring 40 is inserted between each insert 38 and its associated switch contact 16. The springs may be held down at only one end thereof by means of a screw 42 (Figure 3). Alternately, two screws 42 may be utilized, as shown in Figure 3. In the latter case, however, one end of the spring 40 must be slotted as at 44 to accommodate spring deflection. The pressure exerted by the spring is directed toward the screw 32 so that the inserts 38 are always biased away from the switch contacts 16.

From the above description, it is apparent that the novel rotary limit switch arrangement of the present invention is inexpensive to fabricate and maintain and occupies a comparatively small space in a direction radially of the machine tool member driving means, in this instance the shaft 28.

I claim:

1. A limit switch arrangement comprising: a pair of limit switches, a rotatable member therebetween; means to rotate the rotatable member in either direction; a screw rotatably received in said member for movement axially thereof when the member is rotated, said screw having axial extensions .engageable with the limitswitches for. actuating the latter in,respo nse, to rotation of. the member.

2. A limit switch arrangement comprising: a pair of switcheshaving contactimeans facingeach other; arrotatt able member positionedibetween:sQidswitches .and having its; axis substantially, aligned withthe; switch contact means; and ascrew threadab'lyreceived'in said-=member and movable axially thereof when said-member is-rotated.

3}. A switch arrangement for determining the-distance of; travel in opposite directions of amovable member, said, arrangement comprising: a housing; a pair of. opposed .switches mounted-in said housing-and havingcontact means facing and aligned with each other; aworm wheelrotatably carried by said housing between said switches and having its. rotational axis substantially alignedwith said switch contactmeans; a screw thread? ably received in said.worm-wheeland-movable axially thercoi when said; worm wheel is rotated, said: screw having contact portions extending. axially at opposite ends 'ofsaid screw, said portions being nonrotatab'l-y re:- ceived inopenings provided. in said housing, each of said portions being selectively engageable with a related switch contactzmeans when said worm wheel .isrotated; anda worm rotatable proportionally with said. movable member and engaged with saidworm wheel to rotate the latter.

4. A switch arrangement for determining the distance of travel in opposite directions of a movable member, said arrangement comprising: a housing; a pair of'opposed switches mountedin said housing and havingcontactimeans-facing and aligned with each other; a worm wheel rotatably carried by said housing between said switches and having its rotational axis substantially aligned with said switch contact means; a screw threadab-lyreceived in said worm wheel and-movable axially. thereof when said worm wheel is rotated, said screw having contact portions extending axially at opposite ends of said screw, said portions being nonrotatably received in openingsprovided in said housing,. each of said portions being selectively engageable with arelated switch contact-means when said worm wheel is rotated; removable'inserts received in said housing openings adjacent each-contact portion for varying the'.eiiective travel of 5 said screw;'and resilient means for returnin'g saidimse'rts to inoperative position after a switch contact'means has been actuated and the screw motion has been re versed.

5. A switch arrangement...comprising: a housing having a recess open at the top thereof, said recess being non-round in cross-section; a rotatable member journalled in the housing; means in threaded engagement with the member; switch means carried by the housing; extension means fi'xed to. saidfirst-mentioned means and complementary in cross-section to said recess and reccivecl therein; at -least one insert complementary in cross-sectionto-saidireeess and received therein; and a cover removably attached to the housing'closing'the top of said recess; said. insert. being movablev from the top of said recess when the cover is removed from the housmg. I

6. A switch arrangement comprising: a housing having a recess at the top thereof; a rotatable member journalledin said housing; meansmovable by said member axially thereof,.said-means having extension means receivedv insaid recess, at least one insert received in'said recess between. the. extension means and the switch means; and a cover removably attachedtosaid housing and closing the top-of said recess; said insert being removable from said recess upon removal of said cover.

7. A switch arrangement comprising: av housing; a pair of opposed switchesmounted in saidhousing and having actuating means; a. member rotatablymounted in said-housing betweensaid. actuating means; means movable by saidfmember toward. and away from respective switches; at least oneadjustment'insert movably mounted in saidhousing between said movable means and a relatedv actuating means; and a cover removably attached to said housing; said. insert being. removable fromsaid housing upon removal of said cover.

8. A-limit switch-arrangement comprising: a pair of opposed. switches; arotatabie. member; means to rotate the :member in either direction; a screw rotatably received in said member for movement. axially thereof, said screw-having extensions operable, to. actuate said switches when the screw is rotated.

References Cited in the file of this patent UNITED STATES PATENTS.

2,566,824 Carlson Sept. 4, .1951