Note: Descriptions are shown in the official language in which they were submitted.
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CO:LLABl,E RULE CASING
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The present invention relates to a casing for a coilable
rule and, more particularly, to an improved casing structure
including a pair of inner plastic case members received in
a thin outer metal case.
U.S. patents 3,214,8~6 and 3,216,117, assigned ko the
assignee of the pTesent invention, illustrate coilable rules
of the type concerned in this invention. Generally, such
rules include a coilable measuring tape and a coil spring
contained within a protective metal casing. The casing
typically consists of two separate die castings composed
entirely o metal to provide a rugged structure which pro-
tects the rule against damage. The all-metal casing is
relatively expensive to rnanufacture and results in a rela-
tively heavy rule. In addition, frictional contact with the
metal casing results in wear on the movable components of
the rule, especially on the surface of the rneasuring tapé at
the location where it passes through the casing.
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An objective of the present invention is to provide an
improved casing for a coilable rule which provides the same
rugged structure and protective features of the all-metal
casings previously used without the manufacturing expense
associated with a solid metal casing. A primary purpose is
to provide a composite casing consisting of a pair of inner
plastic case members and an outer metal case which has the
necessary toughness to withstand abuse and to remain secureLy
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assembled t1lroughout the useful life of the casing.
In addition, -the invention is in-tended to provide an
improved coilable rule casing which minimizes friction be-
tween the casing and Movable components of the rule to re-
duce wear on the measuring tape It is also intended to ;
provide a coilable rule casing which is lighter in weight and
easier to handle than conv~ntional all-metal casings.
The present in~ention achieves the above object:ives in
a casing for a coilable rule comprising a pair of inner,
plastic case members each having a side wall provided with
an inwardly extending, peripheral flange and adapted to fit
together to provide a hollow chamber for receiving the
measuring tape and coil spring, and a thin, outer metal case
shaped to conform to the exterior configuration of the side
walls and flanges of the inner plastic case members and
adapted to receive the plastic case members in a close fit-
ting relationsnip. Each plastic case member includes a
20 central opening formed in its side wall. The metal case in- :~
cludes a pair of holes formed in its opposite sides in align-
ment with the openings in the plastic case members. A center
post is received in the central openings in the plastic case
members and extends across the hollow chamber for supporting
the measuring tape and coil spring. One end.of the post ex-
tends through one of the holes in the metal case and has an
enlarged head for engaging the side of the metal case adja~
cent to the hole to hold the metal case against the adjacent
plastic case member. '~'he post includes a knurled surface
for engagillo one of the plastic case members in its central
opening to hold tne post firmly in place, The other end of
the post has an inwardly extend:ing axial bore to receive a
screw provided with an enlarged headed end for engaging the
opposite side of the metal case adjacent to the other hole to
nold the metal case against the other plastic case member.
Preferably, a series of knurls are ormed on the center
post adjacent to its enlarged ~lead. The knurls provide firm
engagement between the center post and one of the p:lastic
case members to hold the metal case and plastic case member
in a secure assembly. In addition, the knurls prevent ro- -
tation of the center post wnen the screw is threaded into its
other end in the assembly of the rule.
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In a preferred embodiment of the invention, the outer
metal case comprises a pair of mating case portions, each
naving a side wall and peripheral flange conforming in a
close fitting relationship to the side wall and peripheral
flange of the corresponding inner plastic case member.
Further 7 in accordance with another feature of the invention,
each plastic case member includes a plurality of deformable
ribs provided on the exterior surfaces of its side wall and
peripheral flange for engaging the interior of the metal
case to securely hold the metal case and plastic case members
together and to prevent relative movement therebetween.
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In an alternative embodiment of the invention, an
integral, center post is formed on one of the plastic case
members and extends across the hollow chamber into the
opening provided in the other plastic case member. The post
has an axial bore at its free end. A screw is threadably
received in the axial bore and provided with an enlarged
headed end for engaging the metal case to hold the metal
case and plastic case members together.
The invention achieves a casing for a coilable rule
which is rugged in construction.and light in weight. It
also achieves a composite casing in which the inner plastic
case members are held in firm assembly with the outer
metal case. The use of plastic case members for the interior
of the casing reduces the friction between the casing and
movable components of the rule. As a result, the wear on the
measuring tape is substantially reduced, particularly at the
location where the tape passes through the casing.
The improved casing of this invention substantially
duplicates the configuration of the all-metal casing dis-
closed in U.S. patent 3,216,117. Thus, with respect to more
detailed structural features of the casing, reference
should be made to the specification and drawings of U.S.
patent, 3,216,117.
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The accomyanying drawing illustrates preferred embodi-
ments of the invention and, together with the descriptivn
serves to explain tne principles of the invention.
Eig. 1 is a side elevation of a coilable rule illustrat-
ing the external configuration of a casing constructed in
accordance with the present invention;
Fig. 2 is an enlarged vertical section taken along line
2-2 of Fig. 1, showing the details of the inner plastic case
members, outer metal case, and central post of a preferred
embodiment of the invention;
Figs. 3 and 4 illustrate an alternative embodiment of
the casing; and
Fig. 5 illustrates a plurality of deformable ribs pre-
ferably provided on the exterior surfaces of the inner plas-
tic case members to engage and hold the outer metal case.
Referring to Figs. 1 and 2, a coilable rule embodying
the present invention comprises a casing, generally 10,
which receives a coilable measuring tape 12 and a coil spring
14 for winding the measuring tape into a coiled position
within the casing. The rule also includes a pair of discs
15 (Fig. 2) rotatably Jnounted on casing 10 at opposite sides
of measuring tape 12 and coil spring 14. The pair of discs
serves as a guide for measuring tape 12 and coil spring 14
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to prevent frictional engagernent between the casing and the
edges of the rneasuring tape and coil spring. The structural
details of the discs are described in U.S. patent 3,216,117.
Casing 10 is provided with a mouth (not shown) adjacent
to its bottom wall through which measuring tape 12 passes
when the tape is extended and retracted. The inner end of
measuring tape 12 may be connected to the outer end of coil
spring 14 by a tongue and slot connection (not shown) and
the opposite end of the measuring tape is provided w:ith a
conventional hook 16 (Fig. 1). In addi-tion, a locking
mechanism, generally 18, may be provided, as disclosed and
claimed in ~.S. patent 3,214,836.
The casing of the present invention includes a pair of
inner, plastic case members or inserts 20 and 22 (Fig. 2)
adapted to fit together to provide a hollow chamber for re-
ceiving measuring tape 12 and coil spring 14. Preferably,
each inner plastic case member or insert consists of low-
friction, high-impact plastic material, e.g., black ABS
plastic. Plastic insert 20 includes a side wall 24 provided
with an inwardly extending peripheral flange 26. A central
opening 28, preferably circular, is provided in side wa]l
24 of plastic insert 20. A cylindrical boss 30 extends in-
wardly from side wall 24 and surrounds circular opening 28.An inwardly tapered surface 32 is provided on the exterior
of side wall 24 around opening 28.
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Similarly, plastic insert 22 includes a side wall 34
provided with an inwardly extending, peripheral flange 36,
a central opening 38, and a cylindrical boss 40 ~xtending
inwar~ly from side wall 34 and surrounding opening 38. As
shown in Fig. 2, circular openings 28, 38 and cyl:indrical
bosses 30, 40 are in axial alignment. Each disc 15 includes
an annular hub portion 42 which receives the corresponding
cylindrical boss 30, 40 of the plastic inserts. Plastic
inserts 20 and 22 may be provided with a plurality of rnale-
female connections 44 (one shown) which allow the insertsto fit together in a predetermined orientation to define the
hollow chamber in which measuring tape 12 and coil spring 14
are received. Both inserts can be molded by known techniques.
In accordance with the invention, casing 10 also in-
cludes a thin, outer metal case or skin shaped to conform
to the exterior configuration of the side walls and flanges
of the inner, plastic case members or inserts. Preferably,
as shown in Fig. 2, the thin outer metal case comprises a
pair of mating case portions 50 and 52 which receive plastic
inserts 20 and 22 in a close fitting relationship. Metal
case portion 50 includes a side wall 54 shaped to conform to
the exterior surface of side wall 24 of plastic insert 20 ;
and a~peripheral flange 56 shaped to conform to the exterior
surface of flange 26 of the plastic insert. Similarly,
metal case portion 52 includes a side wall 58 shaped to con-
form to the exterior surface of side wall 34 of plastic
insert 22 and a peripheral flange 60 shaped to conform to the
exterior surface of flange 36 of the plastic insert. `
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Me-tal case portion 50 includes an inwardly tapered,
annular flange 62 which de:fines a circular hole in its side
wall 54 in alignment with circulal opening 38 of plastic in-
sert 20. Si.milarly, metal case portion 52 includes an in-
wardly tapered, annu;lar flange 64 which defines a circular
hole in its side wall 58 in alignment with circular opening
38 of plastic insert 22. As shown in Fig. 2, the hole defi.ned
by annular flange 62 is substantially larger than the hole
defi.ned by annular flange 64.
Metal case portions 50 and 52 may be formed as a thin
steel shell. Preferably, the thin steel is chrome plated to
enhance its durability.
A center post 70, preferably metal, is received in
central openings 28 and 38 provided in plastic inserts 20
and 22. Post 70 extends across the nollow chamber defined
by the plastic inserts to provide a support for measuring
tape 12 and coil spring :L4. The inner end of coil spring 14
may be anchored to post 70. One end of post 70 extends
through the large hole in side wall 54 of metal case portion
50 and has an enlarged head 72 for engaging annular flange
62 to hold the metal side wall against side wall 24 of
plastic insert 20. The other end of post 70 has an axial
bore 74 which, in the preferred embodiment, is internally
threaded.. This end is countersunk to provide an inwardly
tapered, conical surface 76 for receiving annular flange
64 of metal case portion 52.
In the preferred embodiment, as shown in Fig. 2, center
post 70 includes a knurled surface 78 for engagiJIg plastic
insert 20 to hold the post firmly in place. Preferably,
a se-ries of knurls is fo:rmed around t]-le exterior of post 70
adjacent to its enlarged head 72. With post 70 inserted in
opening 28, its knurled surface 78 engages plastic insert 20
along the inner cylindrical surface of boss 30 to hold the
post firmly in place. The knurls secure post 70 to plastic
insert 20 so that side wal] 54 of metal case portion 50 is
held against side wall 24 o:E plastic insert 20. The knurls
also prevent undesired rotation of post 70 relative to
plastic insert 20.
An assembly screw 80 is received in threaded axial bore
74 in center post 70. Assembly screw 80 is provided with an
enlarged headed end 82 for engaging flange 64 of metal case
portion 52 to hold its side wall 58 against side wall 34 of
plastic insert 22.
In a preferred embodiment, a belt clip 90 may be mounted
on the metal case. The belt clip comprises a generally flat,
metal strip bent into the desired shape and provided with
an inwardly tapered, annular flange 92 which defines a
circular hole for receiving assembly screw 80. Headed end
82 of the assembly screw serves to fasten belt clip 90 to
the metal case.
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Referring to ~igs. 3 and 4, :iJI an alternati~e embodi-
ment of the invention, an integral, center post 100 may be
formed on plastic insert 20 in place of the separate post
provided in the preferred embodiment of Fig. 2. The free
end of post 100, which is received in central opening 38
of plastic insert 22, is a~dentical in configuratioll to the
corresponding end of post 70 (Eig. 2~. Accordingly, the
same reference numerals are used to identify the structural
features of post 100.
Initially, the opposite end of post 100, which is
integrally formed as part oI insert 20, includes a cylindri-
cal extension 102 which is received in the hole defined by
annular flange 62 of side wall 54 of the metal case. As
shown in Fig. 4, cylindrical extension 102 may be shaped
into an integral retainer by conventional heating or ultra-
sonic techniques to lock annular flange 62 of the metal case
to plastic insert 20.
Preferably, in the alternative embodiment of Figs. 3
and 4, post 100 may be provided with a hollow bore at its
free end and assembly screw 82 may be a self-tapping screw.
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In accordance with another aspect of the invention,
a plurality of deformable ribs may be provided on the ex-
terior surfaces of the side wall and peripheral flange of
each plastic insert for engaging the interior of the metal
case to securely hold the metal case and plastic inserts
together to prevent relative movement therebetween. As
shown in Fig. 5, which is a greatly enlarged view, a
plurality of deformable ribs 104 may be provided on per-
ipheral flange 36 of plastic insert 22. ~hen metal case
portion 52 is assembled over plastic insert 22, ribs 104 on
peripheral flange 36 are deformed as the ribs move into cvn-
tact with peripheral flange 60 of the metal case. The de-
formed ribs enhance the frictional engagement between the
` plastic insert and metal case portion to securely hold these
components together. Similar deformable ribs may be pro~
vided on all exterior surfaces of plastic inserts 20 and 22.
The present invention is not limited to the specific
details shown and described, and modifications may be made
to the coilable rule casing without departing from the prin-
ciples of the inventinn.
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