US3077101A

US3077101A - Automatic keyhole cover for cylinder locks

Info

Publication number: US3077101A
Application number: US130236A
Authority: US
Inventors: Edward N Jacobi
Original assignee: Briggs and Stratton Corp
Current assignee: Briggs and Stratton Corp
Priority date: 1961-08-07
Filing date: 1961-08-07
Publication date: 1963-02-12
Anticipated expiration: 1980-02-12

Description

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Feb. 12, 1963 E. N. JACOB] 3,077,101 AUTOMATIC KEYHOLE COVER FOR" CYLINDER LOCKS Original Filed Oct. 19, 1959 3 Sheets-Sheet 1 Feb. 12, 1963 E. N. JACOB! 3,077,101

AUTOMATIC KEYHOLE COVER FOR CYLINDER LOCKS Original Filed Oct. 19, 1959 AUTOMATIC KEYHOLE COVER FOR CYLINDER LOCKS Original Filed 001:. 19. 1959 Feb. 12, 1963 N, A Bl 3,077,1 0;

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llnite States Patent Ofilice 3,?7,ll Patented Feb. 12, 1963 Edward N. Jacobi, Wis, assignor to Briggs dz Etratton (Corporation, Milwaukee, Wis, a corporation of elaware Qontinuation of application Ser. No. tldLZflZ, Get. 1%,

195?. This application Aug. '7, 1951, Ser. No. 130,236 lll Claims. (Ci. 7tl-45'5) This application is a continuation of my copending application, Serial No. 347,292, filed October 19, 1959, now abandoned.

This invention relates to key controlled locks and refers more particularly to dust covers for the open end of the keyhole in such locks. The conventional tumbler lock which is widely used in automobiles comprises a cylinder rotatably mounted in a bore in a housing and having a key receiving slot opening to its front end. When such locks are installed in the doors and rear deck lids of automobiles, they are naturally exposed to precipitation, such as rain and snow, as well as to dust and dirt, all of which can injure the lock mechanism, or at least interfere with its operation; and it is therefore desirable to provide a closure or dust cover for the front of the key receiving slot in the cylinder whereby the entry of such foreign matter into the lock mechanism is prevented.

One type of dust cover heretofore used had a cover member hingedly connected to the lock mechanism to swing down over the front of the cylinder. It was necessary to lift the cover member before the key could be inserted into the lock, and this was frequently inconvenient, especially where the person wishing to open the lock was carrying packages and did not have both hands free.

Another type of prior dust cover, illustrated in Patent No. 2,213,814 to E. N. Jacobi, had a closure member that was pivotally connected to the housing for edgewise swinging motion to and from a the front of the cylinder. This dust cover could be swung aside by means of the key, but it was inconvenient because it required the key to be moved laterally before it could be inserted into the lock.

Patent No. 1,965,942 to E. N. Jacobi illustrates a dust cover that could be opened by axial inserting motion of the key. It comprised a cap secured over the front of the cylinder and having an aperture in line with the mouth of the key slot, while a gate-like cover member was mounted directly behind the cap for edgewise sliding motion transversely to the cylinder axis, to and from a position closing the aperture in the cap. The cover memher was spring biased to its closed position, and one side edge of it was beveled to provide a cam surface by which it could be forced sideward, against its bias, by the nose of a key being inserted into the lock.

The angle of inclination of the cam surface on the cover member in the dust cover just described was necessarily a rather shallow one, and therefore a substantial force had to be exerted upon the key to move the cover member sideward to its open position. Since the cam surface translated rearward key inserting force into sideward opening force upon the cover member, friction between the key and the cam surface was very high, and in some cases was almost as great as the sideward camming component, so that the cover member offered very substantial resistance to key insertion. A lock having such a dust cover also tended to be troublesome when the closure was coated with ice since the ice had to be substantially entirely removed in order to permit the cover member to be engaged by the key and forced sideward thereby to its open position.

closed position overlying By contrast, it is an object of the present invention to provide a dust cover for the key receiving slot in a lock of the character described which opens readily in response to axial inserting force upon the key, and which thus requires no preliminary motion to open the dust cover before the key can be inserted into the lock.

Another object of this invention is to provide a keyhole closure or dust cover for automotive door and rear eck locks which can be easily opened when coated with ice, and from which a coating of ice can be readily broken away by means of the key, the shutter portions of the closure being yieldable inwardly to facilitate breaking of the ice by a key jabbed into the key openin A further object of this invention resides in the provision of a dust cover of the character described comprising an apertured cap mounted over the front of the cylinder and a cover member which lies behind said cap and is movable to and from a position blocking the aper ture in the cap, wherein the cover member is normally held in its closed position and is also urged into sealing engagement with the cap by spring means which exerts a forward bias upon the cover member so that the cover iember can be readily displaced to its open position by the nose of a key being inserted into the aperture in the cap.

The invention has for another of its objects the pro vision of a keyhole dust cover of the character described wherein the shutter or cover member may have both sliding and rocking motion to and from its closed position so that no delicate and expensive hinge or pivot is mbodied in the dust cover of this invention, but the movements of the cover member are nevertheless attended by very little friction, thus assuring both easy displacement of the cover member by a key being inserted into the lock and prompt automatic return of the cover member to its closed position when the key is withdrawn. it is also an object of this invention to provide a key slot closure or dust cover of the character described which occupies relatively little space on the front of the lock despite the fact that its cover member is biased forwardly and is adapted to be displaced to its open position by means of a key being inserted straight rearwardly into the key slot.

Still another object of this invention resides in the provision of a key slot closure of the character described, comprising an apertured cap mounted over the front of the lock cylinder and a cover member which lies behind the cap and is movable to and from a position closing the aperture in the cap, wherein spring means reacting between the cover member and the front of the cylinder biases the cover member into sealing engagement with the cap as well as urging it to its closed position, and also biases the cap forwardly into sealing engagement with an annular retaining member by which the cap is rotatably held in place over the front of the cylinder.

With the above and other objects in view which will appear as the description proceeds, this invention resides in the novel construction, combination and arrangement of parts substantially as hereinafter described and more particularly defined by the appended claims, it being understood that such changes in the precise embodiment of the hereindisclosed invention may be made as come within the scope of the claims.

The accompanying drawings illustrate several comlete examples of the physical embodiments of the invention constructed according to the best mode so far devised for the practical application of the principles there of, and in which:

FIGURE 1 is a perspective view of a lock embodying the key slot closure or dust cover of this invention, installed on the rear deck of an automobile, parts of the deck lid being broken away to show the lock;

FIGURE 2 is a fragmentary sectional view taken on the plane of the line 22 in FIGURE 1, but with the rear portion of the lock itself shown in elevation;

FIGURE 3 is a viewsimilar to FIGURE 2 but showing the dust cover being held in its open position by means of a key inserted partway into the lock cylinder;

FIGURE 4 is a fragmentary side view of the lock mechanism shown in FIGURE 1 with portions of the lock housing and lock mounting means broken away and shown in section;

FIGURE 5 is a disassembled perspective view of the dust cover shown in FIGURES 1-4, together with the front portion of a lock on which the dust cover is installed;

FIGURE 6 is a fragmentary sectional view taken substantially on the plane of the line 6--6 in FIGURE 2;

FIGURE 7 is a fragmentary side view of a lock having the dust cover of this invention, with a modified form of rear deck lid mounting for the lock and with portions of the lock housing and its mounting means broken away and shown in section;

FIGURE 8 is a view similar to FIGURE 2 but showing a modified embodiment of the dust cover of this invention on a lock mounted with the lock mounting means shown in FIGURE 7; and

FIGURE 9 is a view similar to FIGURE 8 but showing the dust cover held in its open position by means of a key inserted partway into the lock cylinder.

Referring now more particulmly to the accompanying drawings, in which like numerals designate like parts throughout the several views, the numeral 4 designates generally a cylinder lock mechanism of the type commonly used on automobiles, incorporating a dust cover 5 of this invention, shown installed, by way of example, on an automobile rear deck lid 6. It will be recognized that the dust cover of this invention is also advantageously applicable to locks installed in automobile doors, as well as touc -automotive locks installed in various exposed locations.

As is conventional, the deck lid 6 may comprise spaced apart substantially parallel inner and outer panels 7 and 8, and the lock mechanism may extend through one or both panels. The lock mechanism is of the well known type comprising a housing 9 having a bore 1% opening to its front, and having a cylinder 11 rotatably mounted in the bore. An axially extending slot 12 in the cylinder, opening to the front thereof, is adapted to receive a key 13 by means of which the cylinder may be rotated in opposite directions to defined locked and unlocked positions.

The lock mechanism may be mounted in a variety of ways. As shown in FIGURES 1-4, it is provided at its rear with means defining a forwardly facing shoulder 14 engaged with the inner face of the inner deck lid panel '7, which means may comprise a nut 15 threaded onto the inwardly projecting rear portion 16 of the lock housing. At its front the lock housing has integral radially projecting flange portions 17 at its sides and lugs 18 projecting upwardly and downwardly at its top and bottom. Over the front of the housing is secured a bezel 19 which may comprise an ornamental trim member and which has an opening 19 coaxial with the cylinder and at least as large in diameter. Rearwardly projecting studs 20 on the bezel 19 extend through closely fitting holes in the lugs 18 on the front of the lock housing and have their rear end portions peened over to fasten the bezel to the housing. The bezel overlies the outer face of the outer panel 8 of the rear deck lid and thus cooperate with the nut 15 to prevent axial displacement of the lock housing.

In addition to its function as a lock mounting member, the bezel also cooperates to hold in place on the front of the lock mechanism the dust cover of this invention, which comprises, in general, a dome-shaped cap 21 having a key receiving aperture 22. in line with the key slot 12 in the cylinder, an annular retainer 23 by which the cap is held coaxialwith the cylinder and which provides a if. sealing connection between the cap, the lock housing 9 and the bezel l9, and a pair of cover members 24 which are movable to and from positions in which they close the aperture 22in the cap.

The cap 21, which overlies and is spaced forwardly from the front of the cylinder with its convex surface outward, has a radially projecting substantially planar rim portion 26 around the periphery of its dome-like, substantially hemispherical medial portion 27, and has a rearwardly projecting annular flange 28 around the outer edge of its rim portion. Projecting rearwardly from the flange 23 on the cap are a plurality of narrow fingers 29 which are received in lengthwise extending grooves 39 in the side of the cylinder that open to its front end, thus providing a splined connection between the cap and the cylinder whereby the cap is permitted to have axial translatory motion relative to the cylinder but is constrained to rotate therewith so that the aperture 22 in the cap is always in register with the key slot 12 in the cylinder. To facilitate proper alignment of the aperture 22 in the cap withthe key slot 12 in the cylinder, one of the fingers 29 may be somewhat longer than the others, to be received in a groove in the cylinder that has a correspondingly greater axial length. It will be observed that the cap, including the rim portion 26, the rearwardly projecting flange 28, and the fingers 2%, may be readily formed as a unitary stamping. Because the cap has a substantially larger diameter than the cylinder, the front end portions 25 of the fingers are disposed obliquely to the cylinder axis, converging rearwardly toward one another, and to provide clearance for these portions of the fingers the front of the bore in in the lock housing is divergingly enlarged, as at 50.

The annular retainer 23, which may be formed as a unitary stamping, has a substantially planar flange 32 at itsfront against the rear face of which the rim portion 26 of the cap is engaged, and a larger diameter rearwardly offset rear flange 33, the front face of which flatwise bears against the bezel 1.9, around the aperture 19' therein. A short axially extending portion 34 of the retainer, connecting the front flange 32 and the rear flange '33, embraces the rearwardly projecting flange 28 on the cap to constrain the cap to rotation coaxially with the retainer. A reai-wardly projecting skirt 35 on the retainer embraces the front of the lock housing. Lugs or tangs 36, projecting rearwardly from the skirt 35 of the retainer, at opposite sides thereof, have their rear end portions bent around the flanges 17 of the lock housing,as at 37, to hold the retainer on the lock housing before the latter is secured to the bezel. At its top and bottom the lock housing has forwardly opening arcuate slots 38 in its front face, where the lugs 18 project therefrom, in which portions of the skirt 35 are received.

The cover members 24 overlie the rear concave surface of. the cap and normally cooperate with one another to close the key receiving aperture 22 in the cap. However, they are readily displaceable by means of a key inserted into the aperture, to admit the key to the key slot 12 in the cylinder. Each cover member has a bearing portion 39 with a spherically convex front surface, the radius of which is substantially identical with that of the concave inner or rear surface of the cap. The portions 46 of the rear face of the cap at each side of the aperture 22; therein constitute thrust receiving surfaces which are inclined forwardly and toward the aperture, and the bearing portion 39 of each cover member slidably and rockably rides on one of thesethrust receiving surfaces.

Each. cover member has a shutter portion 41 extending from one side of its bearing portion and disposed at a rearwardly inclined angle thereto, adapted to project radially inwardly beyond the edge of the aperture 22. in the cap. Preferably the shutter portion of each cover memher is rearwardly and radially inwardly inclined when the shutter is'in its closed position, but it could obviously be at such an angle to the cylinder axis as to lie normal thereto when the shutter member is in its normal closed position, the main consideration being that the shutter portion be disposed rearwardly of the edges or" the aperture 2.2 in the cap. The shutter portion terminates in a straight, fiat marginal edge portion that provides a lip 42 which is adapted to fiat-wise abut the lip on the other cover member and cooperate therewith to seal the aperture 22 in the cap.

Each of the cover members is yieldingly biased toward the other, to effect such engagement of their lips, by means of a coiled compression spring 453*, all but the front few coils of which are received in a forwardly opening well in the front portion of the cylinder and the front coil of which engages a rearwardly facing abutment d5 on the cover member. A straight strip integral with the bearing portion of the cover member and extending laterally therefrom at the side thereof remote from its shuttor portion is bent laterally inwardly over the rear of the bearing portion to provide the abutment 45 against which the spring reacts, and a rcarwardly bent end portion of the strip provides a tang or pilot which extends into the coils of the spring to hold it engaged with said abutment. The tongs as are long enough to extend back into the mouths of the wells i t when the cover members are in their open positions to constrain the cover members to rotate with the cylinder, and the tangs also cooperate with the wells in rcsistiru displacement of the coils of the springs out of substantial coaxiality with one another.

The cover members are urged substantially strai -ht forwardly by the springs 43, but because of the forward and radially inward inclination of the thrust receiving surfaces on the cap, the bearing portions of the cover members tend to slide laterally toward one another over said surfaces in response to the biasing force of the springs, and the springs thus serve to hold the lips of the two cover members firmly engaged. Moreover, since the spherical radius of the front surface of the bearing portions of the covers matches the concavity of the thrust receiving surfaces of the cap, the forward bias which the springs exert upon the cover members holds the latter in good surface-to-surface sea g engagement with the when the cover members are in their closed positions. The forward thrust exerted upon the can by the springs, through the cover members, also biases the rim portion 26 of the cap into good sealing engagement with rear face of the front flange 32 on the retainer; and the retainer, in turn, is urged forwardly to firmly the front face of its rear flange 33 against the rear face of the bezel 19, around the marginal edge of the opening 19" therein. The retainer thus provides a seal between the cap, the lock housing and the bezel.

In the lock mounting depicted in FEGURES 7-9, the lock housing has lugs 118 at its top and bottom, the front faces of which are flush with the front of the lock housing and which underlie a panel 168 or the like on which the lock is mounted. Studs 12%, projecting rearwardly from the panel, extend through aligned holes in the lugs lib, and clips M1 on the rear end portions of the studs hold the lock housing against the rear of the panel, with the lock cylinder coaxial with an aperture M9 in the panel. The annular retainer 23 is confined between the panel and the cap, with the front face of the rear flange 33 of the retainer engaging the marginal edge of the panel around said aperture and with the axially extending portion 34 of the retainer piloted in the anerture to hold the retainer coaxial with the aperture and thus with the cylinder. The rim portion 26 on the cap bears against the front flange 32 of the retainer under forward bias exerted by the springs 43 acting through the c ver members, and the retainer thus affords a seal between the cap, the lock housing and the panel whereby the cap is permitted to rotate with the cylinder.

When the cover members are in their closed positions, their shutter portions ll are inclined rearwardly from the edges of the aperture 22 in the cap at a substantially steep angle, as best seen in FIGURE 2, and therefore they may be readily wedged apart by means of a key inserted between them, through said aperture 22. The rearward key inserting force upon the cover members, exerted substantially laterally outwardly upon them because of the inclination of their shutter portions, cooperates with the forward biasing force of the springs to move the cover members slidingly and rockingly on the thrust receiving surfaces 4t) of the cap. Forwardly projecting fingers 52 on the front of the lock cylinder, disposed in pairs at each side of the key slot and extending to within a short distance of the thrust receiving surfaces ill, engage the rear faces of the cover members as the latter are displaced by a key inserted between them and tend to confine the cover members to sliding motion on the thrust receiving surfaces. As the cover members are moved to their open positions, the tangs 45 extend into slot-like spaces 53 be tween the pair of fingers 52 at each side of the key slot. To facilitate such rocking motion of the cover members as is permitted by the fingers 52, the bearing portion of each cover is curved or rounded, as at 47, along its marginal edge portion remote from the shutter. It will be appreciated that the rearward yieldabillty of the shutter portionsmakes it easy to dislodge a coating of ice from the closure, a straight inward jab with the key frequently being all that is necessary to punch the key through the ice and past the shutters into the key slot 12.

When the key is withdrawn, the cover members automatically resume their closed positions under the influence of the springs 43. To insure that the cover members will not be displaced lengthwise of their lips, the bearing portion of each cover member has arcuate flanges 43 along its opposite edges which fiatwise overlie the rear face of the rim portion 26 on the cap when the cover members are in their closed positions and which thus cooperate with the spherical surfaces of the bearing portions and cap to erve as locating means.

Some space is needed between the cap and the front of the lock cylinder to accommodate the rearward component of motion of the cover members, and most of this is provided by the concavity of the cap itself. The retainer 23 also serves to provide such space because its axially offet front flange 32 holds the cap with its rear edge spaced lightly forwardly of the front of the cylinder. The wells i lin the cylinder in which the rear portions of the springs 4-3 are received can have substantial depth, since they are spaced from the sides of the key receiving slot 12 where they do not interfere with the tumbler mechanism, and consequently the springs can be relatively long to provide good biasing action. It will be noted that the springs are substantially steadied by the confinement of their rear end portions in the wells so that they cannot be displaced by any lateral motion of the cover member prior to entry of the rear portions of the tangs 45 into the mouths of the wells.

In the embodiment of the invention shown in FIGURES 8 and 9 there is only one cover member 124, which has a shutter portion 141 wide enough to extend entirely across the aperture 122 in the cap. The lip 142 on the cover member cooperates with a fixed lip 24?; on the cap, defined by an inturned wall portion extending straight back from the aperture 122 along one edge thereof. The fixed lip 242 may, of course, be formed integrally with the cap by bending back the metal struck out of the key receiving aperture 122.

As in the previously described embodiment of the invention, the spring 43 reacts between the bottom of a forwardly opening well 44 in the cylinder and a rearwardly facing abutment 45 on the cover member to bias the cover member forwardly, and the inclination of the thrust receiving surface All on the cap at the side of the aperture 122 remote from the fixed lip translates the forward biasing force of the spring into lateral movement of the cover member to its closed position. The mounting means for the lock mechanism incorporating the dust cover shown in FIGURES 8 and 9 may be the same as that shown in FIGURE 7, and the spring 43 can therefore serve to bias the cap into sealing engagement with the annular retainer 23 and the retainer into engagement with the panel 168 on which the lock mechanism is mounted.

From the foregoing description taken together with the accompanying drawings it will be apparent that this invention provides an automatic dust cover for the key slot of a cylinder lock, wherein the cover is opened by nothing more than mere rearward inserting movement of the key into the key receiving aperture, and which dust cover, because of the absence of any hinge or pivot connections, is inexpensive and simple to manufacture and rugged and dependable in service.

What is claimed as my invention is:

1. In a lock of the type wherein a cylinder having a'key receiving slot opening to its front end is rotatable in a bore in a housing, a closure for the key receiving slot in the cylinder comprising: a cap overlying the front of the cylinder and spaced forwardly therefrom, said cap having portions engaged with the cylinder by which the cap is constrained to rotate in unison with the cylinder, and having a key receiving aperture which is aligned with the mouth of the key receiving slot in the cylinder, said cap also having its rear surface at one side of said aperture inclined forwardly and laterally toward said aperture; an annular member on the front of the housing providing a sealing connection between the cap and the housing which permits the cap to rotate with the cylinder relative to the housing; a cover member having a hearing portion which slidingly underlies the rear surface of the cap at said side of the aperture in the cap, and a shutter portion which extends from the bearing portion at a rearwardly inclined angle thereto and is adapted to project beyond the edge of the aperture, the shutter portion of the cover member terminating in a lip; means carried by said cap providing another lip which opposes the lip on said cover member and is adapted to cooperate therewith to seal the'aperture in the cap; and biasing means reacting between the front of the cylinder-and said cover member to urge the latter forwardly along said inclined surface on the cap, the lateral component of such forward force on the cover member, due to the inclination of said surface on the cap, holding the lip on the cover member in sealing engagement with said other lip, said biasing means being yieidable to permit the cover member to be cammingly propelled, rearwardly and laterally away from said aperture by a key inserted through said aperture and moved rearwardly against the rearwardly inclined shutter portion of the cover member.

2. The key slot closure of claim 1, wherein the rear surface of the cap at the other side of the aperture therein is also inclined forwardly and laterally toward said aperture; wherein said means providing said other lip comprises a second cover member, similar to said one cover member and slidable on the rear surface of the cap at the other side of the aperture in the cap; and wherein other biasing means react between the cylinder and said second cover member to urge the latter forwardly along the rear surface of the cap at said other side of the aperture, and in consequence of the inclination of said surface, laterally toward the first cover member.

3. The key slot closure of claim 1, wherein said means providing said other lip comprises a member fixed on the cap and projecting inwardly along that edge of the aperture in the cap which is remote from said one designated side thereof.

4. In a lock of the type wherein a cylinder having a key receiving slot opening to its front end is rotatable in a bore in a housing, a closure for the key receiving slot in the cylinder comprising: a dome-shaped cap having a medial key receiving aperture and a spherically concave rear surface providing a forwardly and radially inwardly inclined thrust receiving surface at each side of the aperture; an annular member on the housing circumferentially engaged with the cap to hold the cap in front of and spaced forwardly from the cylinder and providing a seal between the cap and the housing which permits the cap to rotate relative to the housing; cooperating means on the cylinder and the cap constraining the cap to rotate in unison with the cylinder, with the aperture in the cap aligned with the key slot in the cylinder; a pair of cover members, each having a bearing portion with a convex surface that slid'ably seats on one of said thrust receiving surfaces on the cap, and a shutter portion extending from the bearing portion and rearwardly inclined thereto, adapted to project beyond the adjacent edge of the aperture in the cap and which terminates in a lip cooperable with the lip on the other cover member to seal the aperture; a rearwardly facing abutment on the bearing portion of each cover member; and a helical compression spring reacting between said abutment on each of the cover members and a forwardly facing surface on the front of the cylinder to urge the bearing portion of the cover member forwardly along said thrust receiving surface of the cap, the lateral compcnents of such forward forces on the cover member-s, due to the inclination of said surfaces of the cap, urging the cover members laterally toward one another to hold their lips engaged, said springs being yieldable to permit the shutter portions of the cover members to be carnmingly propelled rearwardly and apart by a key inserted through said aperture in the cap and moved rearwardly against the inclined shutter portions of the cover members.

5. The key slot closure of claim 4 whereineach of said cover members has an integral elongated strip projecting from the side of its bearing portion remote from its shutter portion, which strip is bent laterally inwardly to overlie the rear of the bearing portion and provide said abutment against which the compression spring engages, and thence rearwardly to provide a tang on which the front coils of the compression spring are piloted.

6. The key slot closure of claim 4 wherein said annular member on the housing has a circumferential flange on its front which overlies the circumferential edge portion of the cap, and against which the cap is maintained sealingly engaged by the forward biasing force of said springs acting through the cover members. k

7. The key slot closure of claim 4, further characterized by the fact that the cylinder has wells opening to its front in which the rearmost coils of the springs are confined and held against lateral displacement.

8. The key slot closure of claim 4, further characterized by the fact that said means for constraining the cap to rotate in unison with the cylinder comprises a plurality of rearwardly projecting fingers on the cap engaged in forwardly opening grooves in the cylinder, so that the cap is free for limited back and forth motion relative to the cylinder.

9. in a lock of the type wherein a cylinder having a key receiving slot opening to its front end is rotatable in a bore in a housing, a closure for the key receiving slot in the cylinder comprising: means providing a cap, connected with the housing and located in forwardly spaced relation to the front of the cylinder and having a key receiving aperture axially aligned with the key slot in the cylinder and a thrust receiving surface which generally faces the cylinder but is inclined forwardly toward the key receiving aperture and extends toward one edge thereof; a cover member having a shutter portion, and a bearing portion which is slidably and rockably engaged with said thrust receiving surface on the cap to mount the cover member for rocking and sliding motion to and from a normal closed position in which its shutter portion projects beyond said one edge of the aperture in the cap and toward the other edge thereof and is disposed rearwardly of said edges; and means on the lock exerting forward bias on the bearing portion of the cover member, whereby the cover member is slidingly urged forwardly along said thrust receiving surface toward said normal closed position thereof, said means being yieldable to permit the cover member to be cammingly moved to a position in which its shutter portion is out of alignment with the aperture and the key slot by means of a key inserted through said aperture and moved rearwardly against the shutter portion of the cover member.

10. The key slot closure of claim 9, further characterized by a finger projecting forwardly from the front of the cylinder to within a short distance of said thrust receiving surface on the cap and which cooperates with said thrust receiving surface to substantially confine the cover member to sliding motion on the thrust receiving surface toward and from said position in which the shutter portion of the cover member is out of alignment with the aperture and the key slot.

11. The key slot closure of claim 4, further characterized by the fact that the cylinder has wells opening 10 to its front in which the rearmost coils of the springs are confined to be held against lateral displacement; and further characterized by a rearwardly projecting tang on each of the cover members engaged in the front coils of the helical compression spring reacting against the cover member, said tangs extending rearwardly a sufiicient distance to engage in the mouths of the wells when the cover members are moved apart by a key inserted between them, to cooperate with the wells in constraining the cover members to rotate with the cylinder.

References Cited in the file of this patent UNITED STATES PATENTS 952,643 Roche Mar. 22, 1910 1,965,942 Jacobi July 10, 1934 2,036,738 Zygrnunt Apr. 7, 1936 2,906,112 Vahlstrorn Sept. 29, 1959 FOREIGN PATENTS 638,078 France Feb. 14, 1928