US3841767A

US3841767A - Follower rod latching device

Info

Publication number: US3841767A
Application number: US00399187A
Authority: US
Inventors: C Little
Original assignee: Weber Knapp Co
Current assignee: Weber Knapp Co
Priority date: 1973-09-20
Filing date: 1973-09-20
Publication date: 1974-10-15
Anticipated expiration: 1991-10-15

Abstract

A file drawer follower rod latching device in the form of a preassembled unit adapted to be fixed to the rear of a wooden front section of a card tray having an opening through which the follower rod extends. The device includes a front section mounted plastic housing having a through stepped bore opening for loosely receiving the follower rod; a metal latch lever permanently fixed to the housing for spring biased pivotal movements transversely of the bore opening into and out of latching engagement with the follower rod; and a coil spring biased spacer sleeve dimensioned to slideably receive the follower rod and tube loosely fitted within the bore opening to accommodate for mounting misalignments of the bore opening relative to the front section opening. The latch lever serves to retain the spacer sleeve within the bore opening during shipment of the latch device from a point of manufacture to a point at which it is to be fixed to the front section and the card tray assembly.

Description

United States Patent [191 Little [111 7 3,841,767 51 Oct. 15, 1974 Primary Examiner-Jerome Schnall Attorney, Agent, or FirmBean & Bean [5 7 ABSTRACT A file drawer follower rod latching device in the form of a preassembled unit adapted to be fixed to the rear of a wooden front section of a card tray having an opening through which the follower rod extends. The device includes a front section mounted plastic hous' ing having a through stepped bore opening for loosely receiving the follower rod; a metal latch lever permanently fixed to. the housing for spring biased pivotal movements transversely of the bore opening into and out of latching engagement with the follower rod; and a coil spring biased spacer sleeve dimensioned to slideably receive the follower rod and tube loosely fitted within the. bore opening to accommodate for mounting misalignments of the bore opening relative to the front section opening. The latch lever serves to retain the spacer sleeve within the bore opening during shipment of the latch device from a point of manu- 1 facture to a point at which it is to be fixed to the front section and the card tray assembly.

8 Claims, 4 Drawing Figures FOLLOWER ROD LATCHING DEVICE BACKGROUND OF THE INVENTION Various types of latch devices have been proposed for use in releasably locking or retaining a follower rod inserted within a card file tray with its front end portion disposed flush with a front surface of the tray, while automatically forcing the front end portion to move outwardly from its flush position upon unlatchingmovements of the latch device in order to permit the front end portion to be readily grasped by a user. As by way of illustration, this general type of latch device has been employed in metal trays, as for example US. Pat. No. 1,918,428; in wooden trays, as for example U.S. Pat. No. 3,405,716 and 3,655,292; and in plastic trays, as for example U.S. Pat. No. 3,658,433 and my US. Pat. No. 3,732,019.

Of these prior latching devices, those including a simple metal spring arranged to bias the follower rod forwardly to a position in which itcan be conveniently grasped are believed most reliable over a long period of use. However, a drawback of such latch devices is that the spring can not be preassembled with the latching parts of the latch device for shipment to a point where it is to be attached to the card tray. Thus, when a card tray is assembled, separate manual operations are required to properly position the latching parts and the spring.

SUMMARY OF THE INVENTION The present invention is directed towards a follower rod latch device including a preassembled spring for biasing the follower rod forwardly to a position in which it canbe grasped by a user.

More particularly, the latch device of the present invention is primarily intended for use with the card trays having wooden front sections where misalignments of the latch device with a follower rod receiving opening formed in the front section are often encountered.

The present latch device comprises a molded plastic housing having a through stepped bore opening for loosely receiving a rearwardly extending end portion of a follower rod and a plurality of apertures for receiving threaded fasteners by which the latch device is fixed to a rear surface of a card tray front section in order to position the bore opening in substantial alignment with a front section opening dimensioned to slideably receive a front end portion of the follower rod. A'portion of the front surface of the housing, which engages the rear surface of the front section, is cut away to define a recess opening transversely of the bore opening and bounded at least in part by a pair of transversely spaced stop surfaces. A follower rod retaining-latch lever is permanently fixed to the housing for pivotal movements within the recess in a direction transversely of the bore opening between first and second positions defined by the stop surfaces; and a spring device is employed to normally bias the latch lever towards its first position, wherein it at least partially overlies the outer or enlarged end of the bore opening. As in conventional constructions, the latch lever is removably receivable within a slot or recess formed in the front end portion of the follower rod in order to releasably retain the follower rod in a fully inserted position.

The latch device of the present invention is completed by the provision of a spacer sleeve, which is loosely" accommodated within the bore opening, and a coil spring, which is disposed between an inner or rear end of the spacer sleeve and an inner or reduced diameter rear end of the bore opening for the purpose of biasing the spacer sleeve forwardly in alignment with the axis of the bore opening for engagement with the latch lever.

The forward end of a spacer sleeve opeing, which is dimensioned to slideably receive the rear portion of the follower rod, is formed with a converging or essentially conically shaped guide-stop surface. This guide-stop surface serves to initially align the spacer sleeve opening with the follower rod when the latter is inserted and thereafter to engage a compression of the coil spring, as the follower rod nears its fully inserted position. By loosely fitting the spacer sleeve within the bore opening, the former may readily tilt or undergo transverse movements relative thereto as required to accommodate for misalignments between the housing bore opening and the front section opening.

In a preferred construction, the parts of the latch device are dimensionsed and arranged such that the latch lever at all times serves to block forward axially directed disassembling movement of the spacer sleeve from within the bore opening, but when manually moved towards its second position allows the spacer sleeve to be removably inserted by tilting same relative to the axis of the bore opening. By this arrangement, the whole of the latch device may be easily assembled as a unit at a point of manufacture and thereafter shipped to a point of use with little likelihood of it becoming disassembled. After the latch device is installedin a card tray, the rear surface of the front section is employed to prevent disassembling movements of the spacer sleeve in cases where the latter has been tilted or displaced sufficiently by the follower rod to otherwise free the spacer sleeve from engagement with the rear surface of the latch lever. A displaced or freed spacer sleeve is returned to a position behind the latch lever automatically each time the follower rod is moved into itsfully inserted position.

DRAWINGS The nature and mode of the present invention will now be more fully described in the following detailed description taken with the accompanying drawings wherein:

FIG. I is a sectional view taken through a library card tray and showing the latch device of the present invention fixed to a rear surface of the tray front-section;

FIG. 2 is an exploded perspective view of the latch device of the present invention in association with the follower rod of the card tray;

FIG. 3 is a sectional view taken generally along line 3-3 in FIG. 1; and

FIG. 4 is a sectional view taken generally along line 44 in FIG. 1.

DETAILED DESCRIPTION Reference is now made particularly to FIG. I, wherein the latch device of the present invention is generally designated as 10 and shown as being employed in association with a library or like card tray 12 having suitably interconnected front and

tray sections

14 and 16, respectively, and a follower rod 18. As with prior constructions, tray 12 defines a latch receiving cavity or chamber 20 to which access can be gained through tray bottom wall opening 22 to permit manual operation of latch for the purpose of releasing follower rod 18 for removal from the tray. It will be understood that, depending upon the construction and material from which the tray sections are formed, cavity 20 and opening 22 may be defined by one or the other of the tray sections or by both, as shown in FIG. 1.

For purposes of illustration, front section 14 is shown as being in the form of a wooden block or panel 24 having a suitably affixed drawer pull 25 and a downwardly and rearwardly opening recess, which cooperates with the front of tray section 16 to define cavity 20 and opening 22; and tray section 16 is shown as being of molded plastic construction.

As is conventional, follower rod 18 is adapted to be removably passed rearwardly through aligned front and

tray section openings

26 and 28, respectively, for the purpose of holding or threadably retaining cards, not shown, within tray section 16. Follower rod 18 includes an enlarged head or front end portion 30, which may be of any desired cross-sectional configuration, and a relatively small diameter rod or rear end portion 32. Head portion 30 includes a forward or front face 34, which for aesthetic reasons is preferably disposed to lie essentially flush with a forward face of the front section, such as the front face of drawer pull 25, when follower rod 18 is in its fully inserted or latched position shown in FIG. 1. Alternatively, the front face 34 may be disposed to lie flush with the front face of block 24. The rearwardly extending end of head portion 30 is formed with a transversely extending recess or groove 40, whichv acts as a keeper for latch device 10, and a rearwardly converging or generally conically shaped surface 42.

Latch device 10 is best shown in FIG. 2 as generally comprisinga housing 50, formed of molded plastic material; a metal latch lever 52; a latch lever mounting rivet 54; a latch lever biasing spring 56; a spacer sleeve 58; and a spacer sleeve biasing coil spring 60. More specifically, housing 50 includes a cylindrically shaped base portion 62, which is formed with a stepped through bore opening 64, having an enlarged diameter front end portion 64a, an intermediate or seat portion 64b, and a reduced diameter rear end portion 64c; and mounting

flange portions

66a and 66b, which extend transversely of base portion 62 adjacent the forward or enlarged diameter end 64a of bore opening 64. Base portion 62 and mounting

flange portions

66a and 66b cooperate to define a housing front surface 68, which is shown in FIGS. 1 and 4 as being clamped in abutting relationship with the rearwardly facing recess bounding surface 24a of block 24 by means of screw fastener devices 70 passing through mounting flange portion apertures 72. Portions of the forwardly facing surface of base portion 62 and mounting flange portion 66a are cut away or removed to define a latch lever receiving recess 74, which opens transversely of bore opening front end portion 640 and is bounded in part by transversely spaced first and

second stop surfaces

76 and 78. The depth of recess 74 in a direction axially of bore opening 64 will of course be sufficient to permit pivotal movements of latch lever 54 in the manner to be described without interference engagement with recess surface 24a.

Again referring to FIG. 2, it will be seen that latch lever 52 includes a central or mounting flange portion 82, which is formed with mounting aperture 84 and a knife-like edge 86; and a pair of

tab portions

88 and 90 which extend at right angles from adjacent opposite ends of flange portion 82. Latch lever 52 is mounted within recess 74 by rivet 54 fitted through aperutres 84 and 91 for pivotal movement transversely of bore opening 64 between first and second positions thereof, which are defined by abutting engagement of latch lever flange portion 82 with

stop surfaces

76 and 78; such positions being designated in FIG. 3 as 52a and 52b, respectively. Spring 56, which is wound around rivet 54 and has its opposite legs engaged with the outer surface of base portion 62 and latch lever tab 88, is employed to normally bias the latch lever into its first position.

Again referring to FIGS. 1, 3 and 4, it will be seen that spacer sleeve 58 is dimensioned to beloosely received within bore opening front end portion 64a and formed with an axially extending through opening including a conically shaped guide or front end portion 92a, an intermediate portion 92b, and a rear end or seat portion 92c.

Seat portions 64b and 92c cooperate to seat or position opposite ends of coil spring 60 with the result that the coil spring tends to maintain sleeve 58 centered within bore opening 64 in addition to opposing rearwardly directed movements of the follower rod, as the latter approaches its fully inserted position. Preferably, spring 60 is of a length sufficient to maintain the front surface of sleeve 58 in frictional abutting engagement with the rear surface of latch lever flange portion 82.

By referring to FIGS. 1 and 4, it will be understood that guide end portion 92a preferably conforms to the shape of head portion surface 42 and that engagement therebetween serves to drive or move spacer sleeve 58 rearwardly against the bias of spring 60, as the follower rod approaches its inserted position. Also, it will be understood that as the follower rod approaches its inserted position rod surface 42 engages latch lever edge 86 whereby to cam the latch lever away from its first position against the bias of the spring 56; such spring thereafter serving to seat edge 86 witin recess 40 when the follower rod is fully inserted, as generally indicated in full line in FIG. 3. When desiring to release the follower rod, an operator merely applies finger pressure to tab portion 90 until edge 86 is removed from within recess 40, whereupon spring 60 acting through sleeve 58 automatically serves to bias or drive the follower rod forwardly from its fully inserted position.

It will be understood that latch device 10 possesses two advantages not found in prior latch devices of which I am aware. First, it permits slight errors in alignment of the latch device with front section opening 26, due for instance to faulty driving of fastener devices 70, to be accommodated for without adversely effecting latch device or follower rod operation. Secondly, it permits follower rod biasing spring 60 to be easily assembled as a part of the latch device at a point of manufacture and the thus assembled unit to be shipped to a point where it is to be fixed to the tray front with little likelihood of the spring becoming disassembled.

The first of the foregoing advantages is made possible by loosely positioning spacer sleeve 58 within bore opening 64 and employing its conically shaped front portion 92a to automatically align the opening of the sleeve with follower rod rear end portion 32, as the follower rod is inserted. By this arrangement the spacer sleeve is free to undergo tilting or transverse movement relative to bore opening 64, as required to accommodate for misalignments between such bore opening and front section opening 26 and/or to accommodate for situations wherein recess surface 24a against which housing 50 is clamped is not disposed perpendicular to the axis of opening 26.

The second advantage is made possible by the fact that spring 56 normally maintains latch lever 52 in its first position wherein it overlies the front end of bore opening 64 to an extent sufficient to block axially directed forward disassembling movements of spacer sleeve 58. However, the spacer sleeve is easily initially assembled within the housing by first moving the latch lever towards its second position and then slightly tilting the sleeve to clear the latch lever as it is inserted. Preferably, spring 60 is of a length sufficient to normally bias the spacer sleeve into engagement with the rear surface of the latch lever in order to maintain the spacer sleeve axially orientated within the bore opening. However, even when spring 60 is not of sufficient length to actually bias the spacer sleeve in this manner, the seating of the spring within seat portions 92c and 64b is helpful to normally retain the spacer sleeve in an essentially axially aligned condition.

I claim:

1. In a card file drawer having front and tray sections; a follower rod removably insertable rearwardly through an opening in said front section, an externally accessible cavity and into said tray section for stringing apertured cards within said tray section, said follower rod having an inner end portion of reduced cross section and an outer end portion of enlarged cross section, said follower rod end portions being joined by a rearwardly facing converging surface, and said outer end portion having a transversely extending groove and being slideably received within said front section opening to position said groove within said cavity when said follower rod is in a fully inserted position; and a latch device fixed within said drawer cavity and having a manually operable member for releasably retaining said follower rod latched in said inserted position by seating engagement within said outer end portion groove, said latch device additionally having a spring deformable by said converging surface upon movement of said follower rod rearwardly towards said inserted position and operable upon manually induced follower rod releasing movements of said latch device member to bias said outer end portion forwardly from said inserted position, the improvement wherein said latch device comprises in combination:

a housing having a stepped through opening with an enlarged front end portion and a reduced rear end portion, said rear endportion being dimensioned to loosely receive said inner end portion of said follower rod, said housing defining first and second stops spaced transversely-of said housing opening;

means for attaching said housing within said cavity to position said housing opening in at least substantial alignment with said front section opening;

said latch device member is a manually operable latch lever mounted on said housing for pivotal movement transversely of said front end portion of said housing opening;

biasing means for normally biasing said latch lever for pivotal movement into a first position determined by engagement of said latch lever with said first stop, said biasing means being resiliently deformable to permit pivotal movement of said latch lever towards and into a second position determined by engagement of said latch lever with said second stop, said latch lever being engageable by said converting surface when said follower rod is inserted thereby to force same to move from said first position against said biasing means towards said second position, said biasing means serving to seat said latch lever within said groove when said follower rod is in said inserted position;

a spacer sleeve loosely fitted within said front end portion of said housing opening, said spring being a coil spring disposed intermediate said spacer sleeve and said rear end portion of said housing opening for resiliently opposing movements of said spacer sleeve theretowards, said coil spring being dimensioned to loosely receive said inner end portion of said follower rod, said spacer sleeve having a through opening including a portion dimensioned to slideably receive said inner end portion of said follower rod and a front end surface portion engageable by said follower rod converging surface for effecting compression of said coil spring upon movement of said follower rod towards said inserted position, characterized in that said loose fit of said spacer sleeve within said housing opening permits-follower rod induced transverse and tilting movements of said spacer sleeve relative to said housing as required to accommodate for misalignments of said housing opening with said front section opening and in that said latch lever when in said first position blocks said front end portion of said housing opening sufficiently to prevent axially directed forward movement of said spacer sleeve outwardly therethrough.

2. The improvement according to claim 1, wherein said rear end portion of said housing opening and a rear end portion of said spacer sleeve define seats for rear and front ends of said coil spring, respectively, whereby said-coil spring tends to maintain said spacer sleeve centered within said housing opening.

3. The improvement according to claim 1, wherein said housing includes a base portion through which extends said housing opening and mounting flange portions, said base portion cooperating with said mounting flange portions to define a front surface of said housing, said front surface being cutaway to define a recess opening in communication with said front end portion of said housing opening for receiving said latch lever, said recess being bounded in part by said stops, said mounting flange portions being apertured to receive said attaching means, whereby said front surface is clamped against a rearwardly facing wall of said cavity through which said front opening extends.

4. The improvement according to claim 3, wherein said coil spring is sized to normally bias said spacer sleeve for movement through said front end portion of said housing opening forwardly of said latch lever.

5. The improvement according to claim 4, wherein said rear end portion of said housing opening and a rear end portion of said spacer sleeve define seats for rear and front ends of said coil spring, respectively, whereby said coil spring tends to maintain said spacer sleeve centered within said housing opening.

6. A manually operable latch device of the type adapted for use in releasably retaining a follower rod in an inserted position Within a card storage tray, said tray being characterized as having a wooden front for defining at least in part an operator accessible cavity in which said latch device is to be disposed for releasably retaining said follower rod in said inserted position, said wooden front being formed with a rearwardly facing cavity bounding wall and an opening extending rearwardly through said rearwardly facing wall for communication with said cavity, said follower rod being characterized as having an enlarged front end portion adapted to be slide fitted within said front opening to extend into said cavity and a reduced size rear porition for stringing cards within said tray, said rod portions being joined by rearwardly facing converging surface, said front end portion being formed with a groove positionable within said cavity when said follower rod is in said inserted position, and said rearwardly facing wall being adapted to receive fastener devices for mounting said latch device within said cavity for latching engagement with said groove when said follower rod is in said inserted position, said latch device comprising:

a housing having a housing opening extending therethrough, a front surface extending transversely of said housing opening, apertures extending rearwardly through said front surface for receiving said fastener devices for clamping said front surface against said rearwardly facing wall to position said housing opening in essential alignment with said front opening, and a recess formed in said front surface to extend transversely of said housing opening, said recess being bounded in part by first and second stops spaced transversely of said housing opening; manually operable latch lever mounted on said housing within said recess for pivotal movement transversely of said housing opening, said latch lever having an edge portion for cooperating with said rearwardly facing converging surface and said groove of said follower rod; biasing means for normally biasing said latch lever for pivotal movement into a first position determined by engagement of said latch lever with said first stop, said biasing means being resiliently deformable to permit pivotal movement of said latch lever towards and into a second position deter mined by engagement of said latch lever with said second stop;

a spacer sleeve loosely fitted within said housing opening, said spacer sleeve having a through opening including a rear portion dimensioned for slideably receiving said inner end portion of said follower rod and a front end portion adapted to be engaged by said follower rod converging surface for effecting rearwardly directed movement of said spacer sleeve within said housing opening when said follower rod is moved rearwardly into said inserted position thereof; and

a spring disposed within said housing opening for resiliently opposing rearwardly directed movements of said spacer sleeve, characterized in that said loose fit of said spacer sleeve within said housing opening accommodates for follower rod induced transverse and tilting movements of said spacer sleeve relative to said housing opening as required to accommodate for misalignments of said housing opening with said front opening and in that said latch lever when in said first position blocks the forward end of said housing opening sufficiently to prevent movement of said spacer sleeve outwardly therethrough and when in said second position partially blocks the forward end of said housing opening whereby to prevent axially directed movement of said spacer sleeve outwardly therethrough while permitting movement of said spacer sleeve outwardly therethrough past said latch lever when said spacer sleeve is tilted relative to said housing openmg.

7. A latch device according to claim 6, wherein said spring is sized to normally bias said spacer sleeve forwardly into engagement with said latch lever.

8. A latch device according to claim 6, wherein a rear end portion of said housing opening and a rear end portion of said spacer sleeve define seats for rear and front ends of said spring, respectively, whereby said spring tends to maintain said spacer sleeve centered within said housing opening.

Claims

1. In a card file drawer having front and tray sections; a follower rod removably insertable rearwardly through an opening in said front section, an externally accessible cavity and into said tray section for stringing apertured cards within said tray section, said follower rod having an inner end portion of reduced cross section and an outer end portion of enlarged cross section, said follower rod end portions being joined by a rearwardly facing converging surface, and said outer end portion having a transversely extending groove and being slideably received within said front section opening to position said groove within said cavity when said follower rod is in a fully inserted position; and a latch device fixed within said drawer cavity and having a manually operable member for releasably retaining said follower rod latched in said inserted position by seating engagement within said outer end portion groove, said latch device additionally having a spring deformable by said converging surface upon movement of said follower rod rearwardly towards said inserted position and operable upon manually induced follower rod releasing movements of said latch device member to bias said outer end portion forwardly from said inserted position, the improvement wherein said latch device comprises in combination: a housing having a stepped through opening with an enlarged front end portion and a reduced rear end portion, said rear end portion being dimensioned to loosely receive said inner end portion of said follower rod, said housing defining first and second stops spaced transversely of said housing opening; means for attaching said housing within said cavity to position said housing opening in at least substantial alignment with said front section opening; said latch device member is a manually operable latch lever mounted on said housing for pivotal movement transversely of said front end portion of said housing opening; biasing means for normally biasing said latch lever for pivotal movement into a first position determined by engagement of said latch lever with said first stop, said biasing means being resiliently deformable to permit pivotal movement of said latch lever towards and into a second position determined by engagement of said latch lever with said second stop, said latch lever being engageable by said converting surface when said follower rod is inserted thereby to force same to move from said first position against said biasing means towards said second position, said biasing means serving to seat said latch lever within said groove when said follower rod is in said inserted position; a spacer sleeve loosely fitted within said front end portion of said housing opening, said spring being a coil spring disposed intermediate said spacer sleeve and said rear end portion of said housing opening for resiliently opposing movements of said spacer sleeve theretowards, said coil spring being dimensioned to loosely receive said inner end portion of said follower rod, said spacer sleeve having a through opening including a portion dimensioned to slideably receive said inner end portion of said follower rod and a front end surface portion engageable by said follower rod converging surface for effecting compression of said coil spring upon movement of said follower rod towards said inserted position, characterized in that said loose fit of said spacer sleeve within said housing opening permits follower rod induced transverse and tilting movements of said spacer sleeve relative to said housing as required to accommodate for misalignments of said housing opening with said front section opening and in that said latch lever when in said first position blocks said front end portion of said housing opening sufficiently to prevent axially directed forward movement of said spacer sleeve outwardly therethrough.

2. The improvement according to claim 1, wherein said rear end portion of said housing opening and a rear end portion of said spacer sleeve define seats for rear and front ends of said coil spring, respectively, whereby said coil spring tends to maintain said spacer sleeve centered within said housing opening.

3. The improvement according to claim 1, wherein said housing includes a base portion through which extends said housing opening and mounting flange portions, said base portion cooperating with said mounting flange portions to define a front surface of said housing, said front surface being cut away to define a recess opening in communication with said front end portion of said housing opening for receiving said latch lever, said recess being bounded in part by said stops, said mounting flange portions being apertured to receive said attaching means, whereby said front surface is clamped against a rearwardly facing wall of said cavity through which said front opening extends.

6. A manually operable latch device of the type adapted for use in releasably retaining a follower rod in an inserted position within a card storage tray, said tray being characterized as having a wooden front for defining at least in part an operator accessible cavity in which said latch device is to be disposed for releasably retaining said follower rod in said inserted position, said wooden front being formed with a rearwardly facing cavity bounding wall and an opening extending rearwardly through said rearwardly facing wall for communication with said cavity, said follower rod being characterized as having an enlarged front end portion adapted to be slide fitted within said front opening to extend into said cavity and a reduced size rear porition for stringing cards within said tray, said rod portions being joined by rearwardly facing converging surface, said front end portion being formed with a groove positionable within said cavity when said follower rod is in said inserted position, and said rearwardly facing wall being adapted to receive fastener devices for mounting said latch device within said cavity for latching engagement with said groove when said follower rod is in said inserted position, said latch device comprising: a housing having a housing opening extending therethrough, a front surface extending transversely of said housing opening, apertures extending rearwardly through said front surface for receiving said fastener devices for clamping said front surface against said rearwardly facing wall to position said housing opening in essential alignment with said front opening, and a recess formed in said front surface to extend transversely of said housing opening, said recess being bounded in part by first and second stops spaced transversely of said housing opening; a manually operable latch lever mounted on said housing within said recess for pivotal movement transversely of said housing opening, said latch lever having an edge portion for cooperating with said rearwardly facing converging surface and said groove of said follower rod; biasing means for normally biasing said latch lever for pivotal movement into a firsT position determined by engagement of said latch lever with said first stop, said biasing means being resiliently deformable to permit pivotal movement of said latch lever towards and into a second position determined by engagement of said latch lever with said second stop; a spacer sleeve loosely fitted within said housing opening, said spacer sleeve having a through opening including a rear portion dimensioned for slideably receiving said inner end portion of said follower rod and a front end portion adapted to be engaged by said follower rod converging surface for effecting rearwardly directed movement of said spacer sleeve within said housing opening when said follower rod is moved rearwardly into said inserted position thereof; and a spring disposed within said housing opening for resiliently opposing rearwardly directed movements of said spacer sleeve, characterized in that said loose fit of said spacer sleeve within said housing opening accommodates for follower rod induced transverse and tilting movements of said spacer sleeve relative to said housing opening as required to accommodate for misalignments of said housing opening with said front opening and in that said latch lever when in said first position blocks the forward end of said housing opening sufficiently to prevent movement of said spacer sleeve outwardly therethrough and when in said second position partially blocks the forward end of said housing opening whereby to prevent axially directed movement of said spacer sleeve outwardly therethrough while permitting movement of said spacer sleeve outwardly therethrough past said latch lever when said spacer sleeve is tilted relative to said housing opening.