Search Images Maps Play YouTube News Gmail Drive More »
Sign in
Screen reader users: click this link for accessible mode. Accessible mode has the same essential features but works better with your reader.


  1. Advanced Patent Search
Publication numberUS2561029 A
Publication typeGrant
Publication dateJul 17, 1951
Filing dateAug 21, 1948
Priority dateAug 21, 1948
Publication numberUS 2561029 A, US 2561029A, US-A-2561029, US2561029 A, US2561029A
InventorsMason George S
Original AssigneeMason George S
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Lock-guarding plug for keyholes
US 2561029 A
Previous page
Next page
Description  (OCR text may contain errors)

y 17} 1951 G. s. MASON 2,561,029


Patented July 17, 1951 UNITED STATES PATENT OFFICE LOCK-GUARDING PLUG FOR KEYHOLES George S. Mason, Long Beach, Calif.

Application August 21, 1948, Serial No. 45,552

This invention relates to a lock-guarding plug for keyholes. More specifically speaking, the invention pertains to a means for plugging the keyholes of locked doors in such a manner as to prevent such doors from being opened by inserting into the lock master or duplicate keys, said plugging means being so constructed that it may be locked within the keyhole, thus preventing its removal except by persons having an extra key which is operable both to lock the device within and to remove it from the keyhole.

Although it is not broadly new to provide a keyhole plugging device, yet there remains room for making important improvements in devices of this kind.

Accordingly it is an object of this invention to provide a simpler device of the above stated kind and one which can be manufactured at a lower cost.

A more specific object is to provide a keyhole plugging device which cannot readily be tampered with and yet one which dispenses with the tumblers heretofore deemed necessary to safeguard against its removal by unauthorized persons.

Other objects, advantages and features of invention will hereinafter appear.

Referring to the accompanying drawing, which illustrates a preferred embodiment of the invention,

Fig. 1 is a side elevation of the keyhole plug provided by this invention, the key for inserting and removing said plug being shown applied thereto.

Fig. 2 is an elevation viewing the structure of Fig. 1 from the opposite side. Both in Fig. 1 and in Fig. 2 the plug is shown in the keyhole-plugging position.

Fig. 3 is a plan view of the structure shown in Fig.1 looking thereat from the plane indicated by line 3-3 on the latter view.

Fig. 4 is an end elevation of the structure shown in Fig. 1, looking thereat from the plane indicated by line 4-1! on the latter view.

The remaining views are on a larger scale, Fig. 5 being an enlarged cross section of the plug carrier, per se, the plane of section being indicated by line 5-5 on Fig. 1.

Fig. 6 is an elevation looking at the outer end of the keyhole plug, separately shown, from the plane indicated by line 66 on Fig. '7.

Fig. 7 is a side elevational and partly sectional view showing the three parts of the device in an exploded relation.

4 Claims. (01. 70-428) Fig. 8 is an end elevation of the inner member of the locking plug looking thereat from the plane of line 8-8 of Fig. 7.

Fig. 9 is a view showing in full lines in vertical section a fragment of a lock casing within the keyhole of which the device is positioned, as shown in side elevation, together with the key by which it is operated, said device being shown in the locked-in position, preparatory to withdrawing the key to the dotted line position of this view.

Fig. 10 is a reproduction of the full line portion of Fig. 9, except that the device is shown turned to its unlocked position, preparatory to being withdrawn from the keyhole by means of its key portion. Also, in this view, a fragment of the barrel portion of the device is broken away in order more clearly to show said key-portion.

Referring in detail to the drawing, the device, as well shown in Fig. 7, comprises three main parts, a keyhole plug proper l0, plug carrier II and key member I2, the latter having a handhold portion [Zn and being utilizable to lock the other two members of the device within and to remove them from the keyhole of the conventional lock structure I3, shown in a fragmentary manner in Figs. 9 and 10.

Said plug proper I0, separately shown in the right hand portion of Fig. '7, comprises a cylindrical stem [5 carrying, preferably integral with it, a locking tongue l6 which is shaped as an elongated right angular triangle the base of which longitudinally abuts one side of said stem, the inclined side of the triangle sloping down to the stem adjacent to the outer end of the latter.

Around the stem I5 extends a fiat-faced bead H which is located about half way between the aforesaid tongue [6 and the outer or key-engaged end of said stem, and spaced slightly away from said bead toward said tongue is a second bead l8 of the same diameter as said bead I1, said beads being provided so as to afford between them a circumferential channel l9 along which travels an internal retaining lug 20 of the aforesaid carrier ll, so that a relative turning movement is permitted between the members In and H without it being possible to separate them.

Beyond its aforesaid beaded portion'the stem ill has a diametrically reduced end portion 2| over which is fittable the barrel portion 22 of the aforementioned key l2. said portion 2'! is longitudinally grooved around its end and along diametrically opposite sides to receive a wire spring 23, one end of which at times tends to spring out of the groove 24 provided therefor into the position shown in Fig. 7 to engage a longitudinal groove 25 within the carrier member H, thus preventing the relative rotation of said members l and II except when the insertion of the key l2 within the barrel 26 causes the free end portion of said spring to seat in the groove said key to rotate also the plug [0 when a notch 29 in the end of the barrel 22 of-the applied keyis fitted around said rise. The lateral extent and circumferential location of said rise will be varied in difierent keys made by the manufacturer, so

that no one key can be used to put into place and remove the different designs of the device.

The barrel 26 of the-carrier II has its midl engitheportionsemi-oircularly-cut awayat'tfl and-from said barrel extends radially andlongitudinally a downwardly directedwing 3|", which supportsthe device when-within the lock structure 13; From one-end of theouter side of said wing extends a tapered-projection 32. The aforementioned groove zfi of the carrier member H ocoupies the greater part of the length of the innor side-portion of said wing- 3 The'key I2 is shown provided, at the open end of its barrel portion, with an external lug 255 which vis insertable into the aforesaid carrier groove 25 with a. working fit.

InHFigssQ and 10- the conventional lock casing structure l3'is shown-having a face portion 27 provided with akey-hole 38, and with an interior verticalipartition 39 having through it a slot 40' the length of which extends vertically.

Inlmanufacturing thedevice, after the plug proper Ii) and its carrier I l have been made the former will be fullyninserted into the latter and then, preferably by the use of a mechanically operatedpunoh, the barrelifi of the carrier willbe indented atthe proper pointto produce internally. thereof the aforesaidlugZ-fl which cooperates i with the channel I9 around the plug to keep the latter in a rotatable but non-withdrawable rela.- tion to thekeeper member It.

, Inoperating the device the user thereorwill first rotationally adjust the assembledplus 4? andaits carrier 5 l to the position shown in Figs. 1 and-2 wherein thetongue it and wing 31 occupy diametrically opposite positions. After this. has been done he will fully. insert the key 12-, which would-otherwise be impossible, for the rotational positionof the key during. insertion is determined by the necessity of its lug 35 registering with the groove 25v of-thecarrier i l-,, and the-rise 28 on they plug; proper mustble so positioned asto enter the. keyqnotch, 29 or else the key cannot be fully ina serted..- .As the key nears its fully insertedposition it swings, the free end portion of the wire spring:

23-outofthe groove 25, thus freeing theplug iii for!rctationain relation to its carrier Il and at the-same time causing.- thekey notch 29 to em brace thecrise: 28 "on the plug. Thereupon; after giving the key ii a half turn, thus bringing the tongue It to the same downwardly directed position as the wing 3|, using said key as a handle, he will insert the device into the keyhole from the inside of the room to be guarded against intruders, and after the device has been inserted to the position shown in 1o he will give the key a vreverse half turnthus bringing the tongue I6 of: the. plug to the upwardly directed position shown in Fig. 9, in which position said tongue will cooperate with the part of the lock casing partition 39 above the slot 40 to prevent an intruder, stationed outside the door from displacing the device from the keyhole. The key 12 may or may not be left within the device until it is desired to remove the latter, which can be done after the key is semi-rotated back to its original position; but if the key is removed the wire spring 23 will spring outlinto thegroove 25' of the carrier II and will positively prevent any intruder from rotating the plug proper in to a position which will turn its tongue to the unlocked position. When the tongue lfi is directed toward the same side of the wing extension 32 said tongue is in a guarded condition, which makes the device more compact and a better article to carry in the pocket.

I claim l. A key operable key hole guard comprising a plu proper of az-generally cylindricalshape: having a radially projecting locking tongue adjacent: to-one of'its ends, said-plug being diametrically reduced throughout :its opposite end portion: and

betweern said two end portions having a channel aroundit, said-plu also having (a radial: rise onone side ofiits said diametrically reduced portion; a carrier for said" plug; saidcarrier: surrounding in an outwardly spaced'manner saiddiametrically' reduced portion of said plug@and-fittingaround said-channeled part thereof, saidi-oarrier-having; an internal projection which-enters said channel thuspreventing separation of the plug and carrier while permittin them to turn'in'relationto each other, said carrier having a radialylongie tudinally extending wing, a portion ofwhich is positionable diametrically opposite to the aforesaid lockingtongue :whenthe device is locked within a keyhole; and askey havinga handheld-at one end and an open barrel at its opposite endfittingwith a rotationalwiit within said carrier and aroundwsaid diametrically reduced portion of saidplug, said key havin an external; lugadjacent to the open-end of: its barreland saidcarrierhaving an internal longitudinal groove. to -admit said lug and a cut-out portion for said luggato. unobstruct turning -.-of theinserted key, the plug proper carrying a-wire springwith'an end port-- tion biased toward" said; groove, whereby the end portion will enter said groove and thus lock-theplug and carrier against relative rotation when the key is withdrawn, theinsertion pfsaid. key

forcingsaid springend out. of said grooventhebarrelportion-of-said key having a notchinsits open end which, when the key is fully inserted;

engagesthe aforesaid radial rise on. the plug proper and renders the'keyusable-to turn the-plug propertaaloeking:positionwhile the latter is within a keyhole.

2. 'Ihesu-bject matter of claim-11,, and theaforesaid diametrically reduced end portion of thepl-ug:

proper having a groove extending across itsend and=-. longitud-inallyalong-sits adjacent diametrically opposit -.'sides said groove seatingthe aforesaid wirespring. p

3. The subject matter of claiml-wherein the cut-out portion for said: lug in the carrier-extends through an angle oi one: hundred. andseig-hty .degrees to permit a halfturn of the fully inserted key when. the latter is 'turned =to:br ing,-.the-1ooking tongue of the plugto a position-diametrically-opposite to the wing of the carriers 4=.=A -key-operable keyhole guard pomprisi-ng an elongated ,plu'gl having, a longitudinal groove in a side thereof and a radial locking--.tongue,-a.

#5 wire spring normally in part contained in said groove, a part of said spring tending to spring out from said groove, a carrier having a barrel surrounding the part of said plug carrying said groove and spring, said barrel having a longitudinal internal groove into which said spring may spring out into, at times to lock said carrier and plug against relative rotation, and a key carrying at one end an open barrel telescoping over the part of said plug furnished with said spring holding the latter retracted to render said plug rotatable within the barrel of said carrier, said key having an external lug which travels along said groove of said carrier during the insertion of the key, said plug having a rise on one side and said key having in its end a notch fitting around said rise to lock said key rotationally to said plug preparatory to using said key to turn REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 87,714 Shepardson Mar. 9, 1869 1,292,696 Brickley Jan. 28, 1919 1,534,745 Stapleton Apr. 21, 1925 1,728,065 Komarcsevits Sept. 10, 1929

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US87714 *Mar 9, 1869 Improvement in key-hole guards
US1292696 *Sep 21, 1918Jan 28, 1919Charles A BrickleyKeyhole-guard.
US1534745 *Dec 29, 1921Apr 21, 1925David A FlemingKeyhole plug
US1728065 *Dec 4, 1928Sep 10, 1929George KomarcsevitsKeyhole guard
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US4391110 *Jul 29, 1981Jul 5, 1983Omco Inc.Barrel lock sleeve
US6227017 *Apr 12, 1994May 8, 2001Darrell A. IgelmundComputer slot security adaptor
US6305199Aug 17, 2000Oct 23, 2001Darrell A. IgelmundComputer slot security adaptor
US6779370Feb 27, 2002Aug 24, 2004Belkin ComponentsSecurity device, method of manufacturing the same, and method of operating the same
US6971254Aug 24, 2004Dec 6, 2005Belkin ComponentsSecurity device, method of manufacturing the same, and method of operating the same
U.S. Classification70/428
International ClassificationE05B17/00, E05B17/16
Cooperative ClassificationE05B17/16
European ClassificationE05B17/16