GB2171453A

GB2171453A - Letter plate lock

Info

Publication number: GB2171453A
Application number: GB08504856A
Authority: GB
Inventors: James Frederic Velloms-Hodgson
Original assignee: Individual
Current assignee: Individual
Priority date: 1985-02-26
Filing date: 1985-02-26
Publication date: 1986-08-28
Also published as: GB8504856D0

Abstract

The lock comprises a L-section elongate member 7 which is mounted on a door 1 such that on upper web 9 extends into its letter plate opening 2. The web 9 has two arms 13, 14 rotatably mounted thereon which, when extending perpendicularly to the axis of the member 7 prevent the letter plate flap 5 from being opened. The arms may be rotated towards the elongate member 7 and into slots 11,12 thus allowing the flap to be opened. The lock may be modified for use with letter plate flaps which are pivotally mounted about a vertical axis. <IMAGE>

Description

SPECIFICATION Letter plate lock This invention relates to a device which is operable to lock a letter plate and thus prevent the letter plate flap from being opened.

Many letter plates comprise a flap pivotally mounted in a frame which is fixed to a door so that in normal operation the flap covers an opening in the door. By virtue of the pivotal mounting of the flap it may be pushed out of the way so that the opening is uncovered and articles such as envelopes may be passed therethrough. The opening and the letter plate together comprise what is commonly known as a letter box.

Letter boxes are clearly very useful to postmen and other persons delivering ordinary mail. However, they may be detrimental to the security of a home. For example, arsonists have been known to start fires in homes by pouring inflammable liquids through letter boxes. Further, would-be thieves and vandals may peer through letter boxes in order to discover whether anyone is at home, prior to breaking in.

A less serious disadvantage of letter boxes is that they are available for any persons to pass unwanted literature such as advertising leaflets therethrough. This is particularly inconvenient for people who are absent from home for long periods.

Thus, it is desirable to be able to prevent a letter box from being opened at certain times, such as at night, or when the occupants of a house are going away for a holiday. (At such times any mail delivered through the post may be collected from the nearest Post Office.) Thus, it is an object of the invention to provide a simple device which may be easily installed for use with existing conventional letter boxes and which is operable to make it impossible to open the letter plate flap from the outside.

According to the invention there is provided a letter-plate lock comprising at least one arm and means for pivotably mounting it in position in the letter plate opening of a door, the arm being movable between an inoperative position in which the letter plate flap is free to open and an operative position in which the opening of the flap is prevented by the arm.

Preferably the arm is pivoted about a vertical axis.

Preferably, the means for mounting the arm includes an elongate member, generally Lshaped in cross-section, comprising an upper web and a lower web, the inner surface of the lower web abutting and being secured to the vertical surface of a door in use, the upper web being horizontally disposed and protruding into the letter plate opening of the door in use and the arm being carried on the upper web.

Preferably, the generally L-section member includes a stepped portion disposed at the corner between the two webs which serves to space the lower surface of the upper web away from the lower surface of the letter plate opening to provide space for the arm to be mounted below said lower surface of the upper web.

In the preferred embodiment, the arm is oriented horizontally and generally perpendicular to the longitudinal axis of the generally L-section member in the operative position.

The arm may be provided with a thickened portion at its end which is furthest from the generally L-section member in the operative position. A person's fingers may easily engage this portion to facilitate rotation of the arm.

In order to enable the arms to retract completely out of the way of the letter plate flap and to provide a neat, flush appearance when the arm or arms are in the inoperative position, a slot may be provided in the upper web and shaped and located such that when the arm is rotated towards the Lsection member the thickened portion may move into and travel along the slot, to a position in which the arm does not protrude laterally beyond the upper web.

In the preferred embodiment, two of said arms are provided, located at positions equally spaced from respective ends of the generally L-section member.

An embodiment of the invention will now be described by way of example only and with reference to the accompanying drawings in which: Fig. 1 is a perspective view of a letter plate lock according to the invention mounted in a letter plate opening of a door, part of the door being shown cut away.

Fig. 2 is a perspective view of the elongate L-section member prior to being installed in the letter plate opening.

Figs. 3(a) and (b) are bottom and side views respectively of the arm.

Referring firstly to Fig. 1 of the drawings a door 1 is shown having a letter plate opening 2 which is covered by a letter plate 3. Letter plate 3 comprises a frame 4 and a flap 5 which is pivotally mounted thereon along its upper edge. A letter plate lock shown generally by the reference numeral 6 is mounted in position in the letter plate opening 2.

The lock 6 includes an elongate member 7, shown in more detail in Fig. 2, which is generally L-shaped in cross-section and comprises a web 8 which is disposed uppermost and horizontally in use and a web 9 which is disposed lowermost and vertically in use.

These are hereinafter referred to as the upper web and lower web respectively. Between the webs 8 and 9 is a stepped portion 10 extending along the full length of the member 7 and having perpendicular elongate surfaces A and B.

Arms 13 and 14 are mounted equally spaced from the opposite ends of the elongate member 7 on the inner or lower surface of the upper web 8. These arms are shown in detail in Fig. 3. The arms may, for example, be die-cast, one end portion 15 being of increased thickness. The other ends of each of the arms are preferably rounded off as shown in Fig. 3 (a), and carry studs 16. Holes 17 and 18 placed at equal distances from opposite ends of the web 8 receive the studs 16 of respective ones of the arms 13 and 14.

Each arm may be rotated about the axis of its respective stud 16 as shown by the arrows in Fig. 1.

Two arcuate slots 11 and 12 are cut in the upper web 8, ending flush with the surface A of the stepped portion 10. These slots are shaped and located such that when the arms 13 and 14 are rotated towards respective slots 11 and 12, the end portions 15 enter and pass along the slots to positions in which no part of either of the arms extends laterally or vertically beyond the upper web 8. The thickened portions 15 act as stops to limit the retraction of the arms into the slots.

The width of the surface A must be equal to or greater than the thickness of the portions of the arms 13 and 14 which slide beneath the upper web 8.

The letter plate lock is mounted in the letter plate opening of a door as follows. After mounting the arms on the upper web 8 as described above, the arms are rotated so that their ends 15 slide into the slots 11 and 12.

The L-section member is then placed against the letter plate opening 2 such that the inner surface of the lower web 7 abuts against the vertical surface of the door and the lower surface B of the stepped portion 10 abuts against the lower surface C of the opening 2 as can be seen clearly from Fig. 1.

The member 7 is then held in this position whilst the arms 13 and 14 are rotated towards their positions shown in Fig. 1. If the arms cannot be easily rotated to positions in which they extend perpendicularly to the longitudinal axis of member 7, a small portion must be cut off from the end 15 of each of the arms sufficient to allow the arms to press tightly against the inside of the letter box flap and so that they can be easily rotated back to their positions in which the ends 15 fit into the slots 11 and 12.

When the length of the arms has been satisfactorily adjusted, the lower web 9 of the elongage L-section member 7 is secured to the door by means of retaining screws. Suitable holes 19 and 20 are provided in the lower web for this purpose.

Clearly when the arms extend perpendicularly to the longitudinal axis of member 7, the letter plate flap cannot be opened by pressure from the outside of the door and thus the arms are in the operative position. However, the letter plate flap may easily be unlocked by rotating the arms towards the centre of the elongate member 7 such that the ends 15 fit in the slots 11 and 12. When the arms occupy positions in which they do not extend laterally or vertically beyond the upper web 8, the arn5s- are in an inoperative position in which the flap can be easily opened.

It will be understood that the purpose of the stepped portion 10 is to allow sufficient room for the central portions of the arms 13 and 14 to slide between the lower surface of the upper web 8 and the lower surface of the letter plate opening.

The elongate member 7 may suitably be 6" (152 mm) long, and the webs 8 and 9 may have widths X and Y of 1" (25.4 mm) and 0.625" (15.875 mm) respectively. The distance S from one end of the elongate member to the edge of the nearest slot measured along the edge of the web 8 may be 1.313" (33.34 mm), and each slot may be 0.625" (15.875 mm) wide. The distance T between the inner edges of the slots as measured along the edge of the web 8 may be 2.125" (54.0 mm). Each of the webs may suitably be 0.125" (3.175 mm) thick. The widths of surfaces A and B may be 0.156" (3.869 mm) and 0.125" (3.175 mm) respectively.

The length Z of the arms may be 1.31" (33.3 mm) and the width W may be 0.25" (6.35 mm). The depth Q of the end portions 15 may be 0.25" (6.35 mm) and their lengths P may be 0.375" (9.525 mm). The depth of the remaining portion of the arm R may be 0.125" (3.175 mm). The studs 16 may suitably be 0.125" (3.175 mm) in diameter, and should be placed in the centres of the rounded end portions of the arms, i.e.

0.0625" (1.5875 mm) from the edges. The holes 17 and 18 may suitably be 0.156" (3.969 mm) in diameter and the distance M between the edges of the holes and the ends of the web may be 0.625" (15.875 mm).

The embodiment of the invention described herein is particularly adapted for use with a letter box of which the letter plate flap is pivoted about a horizontal axis. In a small number of letter boxes, the letter plate flap is pivoted about a vertical axis. The letter plate lock described above could be modified for use with such letter boxes without departing from the scope of the invention.

Claims

1. A letter plate lock comprising at least one arm and means for pivotably mounting it in position in the letter plate opening of a door, the arm being movable between an inoperative position in which the letter plate flap is free to open, and an operative position in which the opening of the flap is prevented by the arm.

2. A letter plate lock as claimed in claim 1 wherein the arm is pivoted about a vertical axis.

3. A letter plate lock as claimed in claim 1 or 2 wherein the means for mounting the arm includes an elongate member, generally Lshaped in cross-section, comprising an upper web and a lower web, the inner surface of the lower web abutting and being secured to the vertical surface of a door in use, the upper web being horizontally disposed and protruding into the letter plate opening of the door in use and the arm being carried on the upper web.

4. A letter plate lock as claimed in claim 3 wherein the generally L-section member includes a stepped portion disposed at the corner between the two webs which serves to space the lower surface of the upper web away from the lower surface of the letter plate opening to provide space for the arm to be mounted below said lower surface of the upper web.

5. A letter plate lock as claimed in claim 3 or 4 wherein the arm is oriented horizontally and generally perpendicular to the longitudinal axis of the generally L-section member in the operative position.

6. A letter plate lock as claimed in claim 3, 4 or 5 wherein the arm is provided with a thickened portion at its end which is furthest from the generally L-section member in the operative position.

7. A letter plate lock as claimed in claim 6 wherein a slot is provided in the upper web and shaped and located such that when the arm is rotated towards the L-section member the thickened end portion may move into and travel along the slot, to a position in which the arm does not protrude laterally beyond the upper web.

8. A letter plate lock as claimed in any preceding claim wherein two of said arms are provided, located at positions equally spaced from respective ends of the generally L-section member.

9. A letter plate lock substantially as hereinbefore described with reference to the accompanying drawings.