United States Patent £191
`Rutty et al.
`
`[11]
`
`(45]
`
`4,429,462
`Feb. 7, 1984
`
`[54] VARIABLE STIFFNESS· RULE BLADE, RULE
`EMPLOYING SAME, AND METHOD OF
`MAKING SAME
`
`[75]
`
`Inventors: Edward C. Rutty, Portland; Carl C.
`Stoutenberg, Burlington, both of
`Conn.
`[73] Assignee: The Stanley Works, New Britain,
`Conn.
`[21] Appl. No.: 430,730
`[22] Filed:
`Sep. 30, 1982
`Int. Cl,3 ................................................ GOlD 3/02
`[51]
`[52] U.S. Cl ....................................... 33/138; 242/84.8
`[58] Field of Search ............................. 33/138, 137 R;
`242/84.8
`
`(56]
`
`References Cited
`U.S. PATENT DOCUMENTS
`950,581 3/1910 Tracy .................................... 33/138
`1,730,199 10/1929 Farrand ................................. 33/138
`2,050,941 8/1936 Farrand ................................. 33/138
`
`2,319,724 5/1943 Dinhofer ............................... 33/138
`2,410,420 11/1946 Bennett ................................. 33/138
`
`FOREIGN PATENT DOCUMENTS
`9823 4/1980 European Pat. Off ............... 33/138
`2902882 1/1979 Fed. Rep. of Germany ........ 33/138
`104305 7/1899 Fed. Rep. of Germany ........ 33/138
`1193809 3/1958 France .................................. 33/138
`Primary Examiner-Willis Little
`[57]
`ABSTRACf
`A coilable measuring blade for coilable rules has a con(cid:173)
`cavo-convex cross section which has an intermediate
`portion with a smaller arc and greater height extending
`through and beyond the normal standout length to pro(cid:173)
`vide greater standout length. The blade may also have
`an outer terminal portion of greater height to require its
`deflection as it enters the rule casing and thereby pro(cid:173)
`vide reduction of the speed with which the blade is
`being retracted into the casing.
`
`25 Claims, 20 Drawing Figures
`
`y
`
`z
`
`APEX TOOL GROUP, LLC - EX. 1008-001
`
`

`

`U.S. Patent Feb. 7, 1984
`
`Sheet l of 2
`
`4,429,462
`
`18
`
`28
`
`26
`
`FIG.!
`
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`10
`
`FIG.7
`
`60
`
`APEX TOOL GROUP, LLC - EX. 1008-002
`
`

`

`U.S. Patent Feb. 7, 1984
`
`Sheet 2 of 2
`
`4,429,462
`
`X
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`
`APEX TOOL GROUP, LLC - EX. 1008-003
`
`

`

`1
`
`4,429,462
`
`2
`Various cross sections have been used for the conca(cid:173)
`vo-convex blade construction. Generally, the cross
`section is a segment of a circular arc or a segment of a
`circular arc with straight segments at its ends (e.g, recti(cid:173)
`linear portions which are tangential to the center arcu(cid:173)
`ate segment). In this manner the concavo-convex cross
`section will not have any sharp bends which would
`produce points where the blade will be overstressed
`during the repeated flattening operation, and the
`amount of force required to flatten the curve is more
`readily available from economically utilizable power
`return springs.
`It is an object of the present invention to provide a
`novel coilable metal blade for a rule which provides
`greater standout length.
`It is also an object to provide such a blade which can
`be readily and economically fabricated and which will
`enjoy long life.
`Another object is to provide such a blade which will
`slow the rate of retraction as the blade is almost fully
`retracted into the casing.
`A further object is to provide a novel rule employing
`such 11-"blade and which may be fabricated readily and
`relatively economically.
`Yet another object is to provide a novel method for
`fabricating such coilable metal rule blades offering en(cid:173)
`hanced or great standout.
`
`VARIABLE STIFFNESS RULE BLADE, RULE
`EMPLOYING SAME, AND METHOD OF MAKING
`SAME
`
`25
`
`BACKGROUND OF THE INVENTION
`The present invention relates to coilable rules and
`more particularly to such rules employing coilable
`metal blades with greater standout length when unsup- 10
`ported as extended from the casing.
`Coilable metal rules are widely used and frequently
`employ a concavo-convex cross section or other cross
`sectional configuration which will stiffen the blade so
`that the user may singlehandedly bridge a distance with 15
`the blade tip extended in a straight line. This enables the
`user to bridge doorways, shaftways, excavations and
`the like with the unsupported blade. It is known that the
`degree of curvature or cross section will influence and
`substantially determine the standout length (the length 20
`of the blade which can be extended unsupported with(cid:173)
`out collapsing at the support point) or breakpoint (the
`point at which the unsupported rule will collapse) for a
`rule of any particular width, thickness and metal char(cid:173)
`acteristics.
`Such blades are generally used in power returnable
`coilable rules that include a coiled spring which has the
`effect of retracting the extended blade into the rule
`housing or casing wherein it coils about the reel in its
`retracted position. It will be appreciated that the conca- 30
`vo-convex cross section of the blade is flattened as it is
`coiled within the rule casing, whether by manual action
`or by the retracting effect of such a power return
`spring. The stiffer the blade, the more spring power
`required to effect such flattening of the blade upon 35
`retraction.
`As is also well known, blades employing such a con(cid:173)
`cavo-convex cross section generally must be heat
`treated to achieve the desired flexural characteristics to
`withstand the repeated flattening operation that occurs 40
`in the coiling of the blade within the rule casing. It has
`been necessary to balance the advantages to be ·gained
`by increasing the depth of curvature of the blade for
`increased length of blade standout with the power re(cid:173)
`quirements for the spring to effect its retraction and also 45
`with the life characteristics resulting from repeated
`deflection into the flattened condition when the blade is
`coiled.
`Moreover, because the extended blade will assume
`the concavo-convex cross section, the indicia which are 50
`imprinted thereon become more difficult to read when
`the arcuate cross section becomes steeper. Lastly, when
`there is a very high cross curve or deep cross section,
`there is a stress point at the point where the blade does
`buckle when fully extended, which, over repeated us- 55
`age, may cause a stress fracture.
`Because of the necessity for balancing these various
`factors, the range of average standout lengths for com(cid:173)
`mercially available widths of concavo-convex blades is
`set forth in the following table:
`
`SUMMARY OF THE INVENTION
`It has: now been found that the foregoing and related
`objects may be readily attained. in a coilable rule blade
`providing greater standout length and comprising an
`elongated strip of resiliently deflectable metal having a
`substantially uniform width in its coiled flattened state
`and, in its uncoiled state, a concavo-convex cross sec(cid:173)
`tion along substantially its entire length. This concavo-
`convex cross section has a central segment of arcuate
`configuration defined by a radius R and has a depth H.
`The blade has a first portion adjacent one end thereof
`having a depth H1 and a radius R1, a second portion
`which extends from the first portion and has a depth H2
`and a radius Rz, and a third portion which extends from
`the second portion to adjacent the other end with a
`depth H3 and a radius R3. The depth H2 of the second
`portion is greater than the depth H1 and H3 of the first
`and third portions, and its radius R2 is less than the radii
`R1 and R3 of the first and third portions. The second
`portion extends for. a portion of the length of the blade
`including the normal breakpoint for a blade of that
`width and having a uniform cross section correspond(cid:173)
`ing to the depth H1 and radius R1 of the first portion,
`and the second portion continues beyond such break(cid:173)
`point towards the other end of the blade to provide the
`greater standout length.
`In its preferred form, the entire cross section of each
`of the blade portions is defined by a single continuous
`arc of the respective radius, or the cross section of each
`of the blade portions includes substantially rectilinear
`segments tangential to the ends of the central arcuate
`segment.
`Conveniently, the depth H3and radius R3 of the third
`blade portion are substantially equal to the radius R1
`and depth H1 of the first blade portion. The radius R2
`and depth Hz of the segment in the second blade portion
`65 is conveniently substantially uniform over substantially
`the entire length of the second portion for ease of fabri(cid:173)
`cation. However, a highly effective structure is one in
`which the radius R2 of the arcuate segment of the sec-
`
`60
`
`BLADE WIDTH, INCHES
`
`STANDOUT LENGTH, INCHES
`12-16
`35-43
`55-73
`86-97
`
`APEX TOOL GROUP, LLC - EX. 1008-004
`
`

`

`4,429,462
`
`3
`4
`ond portion decreases in length and the depth H2 in(cid:173)
`BRIEF DESCRIPTION OF THE ORA WINGS
`creases from the first portion towards the third portion
`FIG. 1 is a elevational view of a power returnable
`of the blade. In such an embodiment, the decrease in
`radius R2 and increase in depth H2 in the second portion
`coilable rule embodying the present invention with a
`portion of the housing end wali broken away to reveal
`is preferably at a substantially uniform rate over sub-
`stantially the entire length of the second portion. How-
`internal construction;
`ever, the radius R2 of the second portion most desirably
`FIG. 2 is a side elevational view thereof with the end
`hook in phantom line for clarity of illustration of the
`increases, and the depth H2 correspondingly decreases,
`at arapid rate adjacent the third portion so as to blend
`exit aperture in the housing;
`FIG. 3 is a fragmentary elevational view of the rule
`thereinto. In one embodiment, the blade has a terminal 10
`portion adjacent its one or outer end which has a radius
`with the blade partially extended from the housing;
`FIG. 4 is a partially diagrammatic cross sectional
`R.; for its arcuate segment which is smaller than the
`view of the blade at the line 4-4 of FIG. 3 with the
`radius R 1, and it correspondingly has a depth H4greater
`than the depth H,, of the first portion of the blade.
`housing exit aperture shown in phantom line and with
`The blade is used in a coilable rule assembly which 15 the blade cross section shown in full line as deflected for
`includes a casing having end walls and a peripheral
`passage therethrough and in phantom line before such
`deflection;
`sidewall defining a chamber therebetween and in which
`FIG. 5 is a similar diagrammatic sectional view of the
`5 5 ·
`the sidewall has an exit aperture therethrough. As is
`bl d
`th h
`·
`·t
`t
`t th 1-
`e ousmg ex1 aper ure;
`a e a
`e me - m
`conventional, the coiled rule blade in the chamber has 20
`FIG. 6 is a similar diagrammatic sectional view of the
`one end extending outwardly of the casing aperture.
`blade at line 6-6 in the housing exit aperture;
`The rule assembly will generally include a coiled power
`FIG. 7 is a fragmentary side elevational view of an-
`return spring within a reel in the chamber and which
`other embodiment of rule using guide rollers in the rule
`has its outer end engaged with the inner end of the blade
`housing for the blade adjacent the exit aperture and
`which is coiled thereabout.
`25 with the blade shown in section;
`In one embodiment, the rule casing cooperates with a
`FIG. 8 is a fragmentary side elevational view of the
`blade having a deeper cross section for its outer end
`blade showing the several portions thereof;
`portion and has an exit aperture which is of a depth Hs
`FIGS. 9-U are sectional views thereof along the
`less than the depth H4 of the terminal portion of the
`section Jines 9-9, 10-10 and 11-11 of FIG. 8;
`blade so as to cause deflection thereof as it passes there- 30
`FIG. 12 is a fragmentary side elevational view of
`through to reduce the rate of retraction of the blade
`another blade embodying the present invention;
`under the action of the power return spring.
`FIGS. 13-19 are sectional views thereof along the
`In making the coilable rule blade, a length of resil-
`section lines 13-13, 14-14, 15-15, 16-16, 17-17,
`iently deflectable metal strip having a width W is pro-
`18-18 and 19-19 of FIG. 12; and
`vided, and the blade is formed to provide in a first por- 35
`FIG. 20 is a cross sectional view of another embodi-
`tion of the length a concavo-convex cross section hav-
`ment of blade employing a modified cross section.
`ing a central segment of arcuate configuration defined
`DETAILED DESCRIPTION OF THE
`by a radius R, and having a depth H1. A second portion
`ILLUSTRATED EMBODIMENTS
`of the length is formed into a concavo-convex cross
`Turning first to FIGS. 1 and 2, therein illustrated is a
`section having a central segment of arcuate configura- 40
`tion defined by a radius R2 and having a depth H2, and
`power returnable coilable blade embodying the present
`the radius R2 is less than, and the depth H2 is greater
`invention and having a housing generally designated by
`than, R 1 and HJ, respectively. A third portion of the
`the numeral10 with end walls 12 and a peripheral side-
`length extending from the second portion is formed into
`wall 14 extending therebetween and in which there is
`a concavo-convex cross section having a central seg- 45 provided an exit aperture 16. The walls 12, 14 define an
`ment of arcuate configuration defined by a radius R3
`internal cavity in which there is a hub 18, and a coiled
`and having a depth H 3, with the radius RJ being greater
`power return spring 20 thereabout which has its outer
`than, and the depth H3 being less than, R2 and Hz, re-
`end secured to the inner end of the blade generally
`designated by the numeral 22 and which is coiled about
`spectively.
`50 the reel 21. The terminal portion of the blade 22 extends
`through the passage 24 and outwardly of the exit aper-
`The forming step may be by a cold forming technique
`in which the length is hardened and tempered and
`ture 16. As is conventional, a hook 26 is provided at its
`thereafter roll formed to shape the several portions of
`end which abuts the sidewall 14 about the aperture 16
`the length into the desired cross section, or by a hot
`and limits movement of the blade 20 inwardly of the
`forming technique in which the heated blade is roll 55 housing 10.
`formed, quenched and tempered. Conveniently, the
`Also shown is a blade locking lever 28 which cooper-
`several portions of the length of metal strip are formed
`ates with mechanism (not shown) within the casing to
`initially in a roll forming operation in which the length
`hold the blade 20 in an extended position as originally
`is passed through a series of roll forming dies providing
`illustrated and described in Robert F. West U.S. Pat.
`a constant configuration for the several portions, and 60 No. 3,214,836 granted Nov. 2, 1965.
`thereafter the second portion is further formed to the
`Turning next to FIGS. 8-11, therein fragmentarily
`desired configuration. If so desired, a section of the
`illustrated are the several portions of an uncoiled blade
`length of strip at the end of the first portion which is
`generally designated by the numeral 30 and which is of
`spaced from the second portion may be formed into a
`substantially uniform width in its flattened or coiled
`concavo-convex cross section having a central segment 65 condition and of concavo-convex cross section in its
`of deep arcuate cross section defined by a radius R4 and
`relaxed or extended position. The outer or first end
`a depth H4 respectively lesser and greater than R1 and
`portion 32 of the blade 30 has an arcuate cross section
`defined by a radius R1, and it has a depth or height H1.
`H 1.
`
`APEX TOOL GROUP, LLC - EX. 1008-005
`
`

`

`4,429,462
`
`5
`6
`return spring to provide a braking action, thus reducing
`The intermediate or second portion 34 is also of arcuate
`the impact force on the hook when it abuts the rule
`cross section which is defined by a smaller radius R2,
`casing.
`thus resulting in a greater depth H2. The inner or third
`Turning now to FIG. 7, the rule of this embodiment
`portion 36 is also of arcuate cross section defined by a
`includes a pair of rollers 64 inside the housing 10 adja.
`radius R3 of greater length than R2 and which is of
`cent the upper side margins of the exit aperture 16 so
`lesser height H3 than the height H2 of the intermediate
`that the terminal portion 62 of the blade 60 is guided
`portion 34. In each of the several portions, the arcs open
`thereby and more readily deflected with less friction
`in the direction of coiling of the blade.
`between the blade 60 and the wall of the casing 10 about
`Diagrammatically indicated by the dimension line
`X-Y is the normal standout length for the blade were it 10 the exit aperture 16. This improves the efficiency of the
`return spring when such braking action is desired, par-
`to have a uniform cross section equal to that of the first
`portion 32 throughout that length. As seen, the interme-
`ticularly when only a short length of the blade. 60 has
`diate portion 34 of greater depth commences prior to
`been extended.
`As bas been previously indicated, the cross section of
`the point Y and extends therebeyond toward the other
`or inner end of the blade 30. As a result of the increased IS the blades of the present invention may comprise a
`continuous circular arc defined by a single radius, a
`stiffness provided by the cross. section of the second
`portion 34 in accordance with the present invention, the
`curvilinear arc. defined by a central arcuate segment of
`standout length for the extended blade is signified by
`one radius and outer arcuate segments of another radius,
`or a composite of a central arcuate segment and rectilin-
`the dimension line X-Z.
`. In this embodiment, the radii Rt. R2 and R3 are sub- 20 ear segments tangential to the ends of the arcuate seg-
`stantially constant throughout their respective portions,
`ments. From convenience and life standpoints, continu-
`except at the ends of the portion 34 where some taper-
`ous circular arc and arc/tangent composite configura-
`ing is present. As a result, the height Ht. H2and H3 of
`tions are preferred.
`the blade 30 is substantially constant in each. of the
`The increase in curvature and depth in the intermedi-
`several portions 32, 34 and 36.
`25 ate portion may be effected by a gradual uniform in~
`Turning now to the embodiment of FIGS 12-19, the
`crease to a point beyond the new breakpoint, or by a
`blade generally designated by the numeral 40 has a first
`series of discrete incremental steps in radius change, or
`or outer portion 42, a second or intermediate portion 44,
`by a single incremental increase to produce a deeper
`a third or inner portion 46, and an outer terminal por-
`cross section which is substantially uniform over the
`tion 48 adjacent the hook As in the instance of the prior 30 entire length except for tapering at the ends thereof.
`From cost and manufacturing standpoints, a single in-
`embodiment, the first portion 42 has a radius Rt and a
`height Ht; and the third. portion 46 has a radius R3 and
`crement is most easily effected; however, a gradual
`a height H3. Iri this embodiment, the radius· R2 of the
`increase, or a series of incremental steps, is desirable
`from the standpoint of minimizing the overall increase
`arcuate ·cross section in the intermediate portion 44
`progressively ·and gradually decreases in· length as 35 in stiffness and attendant increase in spring power re-
`shown by· the radii Ria,· R2b. R2c over substantially its
`quired to effect flattening during retraction.
`The length of the radii in, and the heights of, the
`entire length and then rapidly increases in ·length adja-
`cent the third portion • 46 as· shown by the radius Ru,
`concavo-convex cross section, will vary with the metal
`with attendant variation in the height of the cross sec-
`employed, the width of the strip, the physical character-
`tion as shown by H2o, H2b; H2c and Hu. This gradual 40 istics of the metal, etc. Such radii and heights will be
`readily apparent to those having ordinary skill in this art
`increase in height and stiffness avoids an abrupt change
`with the teaching of this specification before them. It
`and'. increases the stiffness as the standout length in-
`creases, as shown by the standout dimension lines X-Y
`will be appreciated that excessive stiffness in cross sec-
`tion is to be avoided because of its detrimental effect
`and X-Z which are similar in significance to those uti·
`lized in the prior embodiment. In this embodiment, the 45 upon the return spring power requirements and upon
`life of the blade. Accordingly, the intermediate cross
`terminal pOrtion 48 adjacent the hook has a cross 8ec-
`tion with a relatively 'large depth H4 and small radius
`section with its increase should not be overly extended
`R4, as seen in FIG. 19, and which will provide braking
`in length but should encompass a distance beginning at
`about 70-90 percent or the normal standout length and
`action as will be described hereinafter.
`Turning now to the embodiment of FIG. 20 the cross so ending at about 105-120 percent of the enhanced stand·
`section of the blade 50 has a central arcuate segment 52
`out length.
`defmed by the radius R and rectilinear end portions 54
`The methods employed for forming the blade will
`which are tangent to the ends of arcuate segment 52.
`generally involve a hot forming operation to effect a
`This type of cross section is highly effective and rela·
`substantially uniform cross section over the entire
`tiveJy· easily formed.
`SS length of the strip, followed by tempering, . or a cold
`The braking action of the blade embodiment 60 pro-
`forming operation followed by stress relieving. Roll
`viding a terminal portion 62 with a deep cross section
`dies are preferably used in conjunction with elongated
`Ht is illustrated in FIGS. 3-6. As seen in FIG. 4, the
`strip intended to be severed into the desired lengths for
`height Ht of the relaxed terminal portion 62 is greater
`the individual blades, although brake forming of the
`than the depth H2 of the exit aperture while that of the 60 severed lengths may also be employed.· The severed
`adjacent first portion as shown in FIG. 5 and that of the
`blade lengths are then further formed to provide the
`intermediate portion as shown in FIG. 6 are less than
`increased curvature in the intermediate portion, either
`that of the depth H2. As as result, when the blade 60 is
`by a brake forming die and mandrel assembly or by a
`roller die assembly depending upon the type of increase
`being retracted by the return spring, the terminal por-
`tiori 62 must be deflected froin the phantom line show- 65 desired. Brake forming of the severed lengths which
`havebeen previously uniformly formed has been found
`ing to the solid line showing in FIG. 4. The friction and
`spring power consumption required for such deflection
`to be readily added to the existing manufacturing opera-
`slows the rate of retraction under action of the power
`tions.
`
`APEX TOOL GROUP, LLC - EX. 1008-006
`
`

`

`4,429,462
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`20
`
`7
`8
`then'back bending. As will be appreciated, the resultant
`Although the increased depth of cross section in the
`outer terminal section illustrated in one of the embodi-
`blade is relatively free from stresses and relatively stable
`in an extended position.
`ments will have the effect of increasing the frictional
`Following the stiffening operation, the cut off blade is
`resistance to retraction and thus augment braking ac-
`found to have a standout length of about 112 inches as
`tion, it will be appreciated that it also increases the·
`compared to a standout length of about 60 inches for
`power requirement for retracting the extended blade if
`blades of uniform cross section, i.e., which are not sub-
`the length extended comprises only such terminal sec-
`jected to the additional forming step.
`tion. Thus, some manual assistance may be necessary to
`Thus, it can be seen from the foregoing detailed de-
`augment the spring force. To some extent, this problem
`may be reduced by employing friction reducing rollers lQ. scription and the attached drawings that the blades of
`inside the case adjacent the exit aperture and by using a
`the present invention provide rule blades having in-
`low friction synthetic resin insert to define the exit aper-
`creased standout length and that they may be fabricated
`ture as shown in the illustrated embodiment; The length
`readily and relatively economically. Moreover, they
`of this braking section should not exceed about eighteen
`enj6y relatively long life in operation and may be uti-
`inches and preferably comprises the first 6-12 inches of 15 lized in conventional power returnable rules. In accor-
`the blade length. Conveniently, its arcuate cross section
`dance with one aspect, the blades are also provided
`is of a depth about 5-15 percent greater than the height
`with. a braking section adjacent their outer end to re-
`of the exit aperture in the casing.
`duce the impact upon the blade hook or the like.
`Having thus described the invention, we claim:
`1. A coilable rule blade having greater standout
`length comprising an elongated strip of resiliently de(cid:173)
`flectable' metal having a substantially uniform width in
`its coiled" flattened state and, in its uncoiled state, a
`concavo-convex cross section along substantially its
`entire length with the arc opening in the direction of
`coiling, said .blade being relatively free from stresses and
`reh!tively stable in the extended position, said cross
`section having a central segment of arcuate configura(cid:173)
`tion defined. by a radius R and having a depth H, the
`length of said blade being comprised of three portions,
`a first portion adjacent one end thereof with a depth Ht
`and ra:dius.Rt, a second portion extending from said first
`portion with a depth H2 and. a radius R2, and a third
`portion ex\ending from said second portion to adjacent
`the other end thereof with a depth H3 and a radius R3,
`said second portion having a depth H2 greater than the
`depth '}::1,1 ,and . H3 of said first and third portions and a
`radiusJhless than the radii Rt and R3 of said first and
`third portions, said second portion extending for a por(cid:173)
`tion of the length of said blade which includes the nor(cid:173)
`mal breakpoint for a blade of said width and of a uni(cid:173)
`form cross section corresponding to the depth .H 1 and
`radius Rt of said first portion and which extends beyond
`said normal breakpoint towards said other end of said
`blade to provide greater standout length.
`2. The coilable rule blade of claim 1 wherein the
`entire cross section of each of said portions is defined by
`a single continuous arc of the respective radius.
`3. The coilable rule blade of claim 1 wherein the cross
`section of each of said portions includes substantially
`rectilinear segments tangential to the ends of said cen(cid:173)
`tral arcuate segment.
`4 .. The coilable .rule. blade of claim 1 wherein the
`d~pth H3 and radius· R3 ofsaid third portion are substan(cid:173)
`tially equal to the radius Rt and depth Ht of said first
`portion.
`5. The coilable rule blade of claim 1 wherein said
`radius R2 and depth H2 of said second portion are sub(cid:173)
`stantially uniform over substantially the entire length of
`said· second portion ..
`6. A coilable rule blade having greater standout
`length comprising an elongated strip of resiliently de(cid:173)
`flectable metal having .a substantially uniform width in
`its coiled flattened state and, in its uncoiled state, a
`concavo-convex transverse cross section along substan(cid:173)
`tially. its entire length, said cross section having a cen(cid:173)
`tral segment of arcuate configuration defined by a ra(cid:173)
`dius R and having a depth H, said blade having a first
`
`EXAMPLE ONE
`Exemplary of the method of making such blades is
`the following process used for the generation of a' 1 inch
`wide blade having increased standout length.
`Steel strip of SAE 1095 alloy is spheroidized annealed
`and lightly rolled to prevent kinking, and has a Rock- 25
`well B hardness of97--99. The steel strip has a widthcof
`one inch and a thickness of 0.0045 inch ( + or -'-0.0003
`inch).
`The annealed strip is then heated to a temperature of
`about 1550° Fahrenheit in a continuous strip form and is 30
`passed through forming dies which form the strip into
`the desired cross section which is uniform along its
`length. Thereafter, the strip is quenched and cooled to
`fix the configuration so generated, passed through a
`furnace wherein its temperature is raised to about 700° 35
`Fahrenheit to effect tempering and .relieve brittlenes~?,
`and thereafter cooled. At this time, the strip is found to
`have a cross section with a arcuate center section de"
`fined by a radius of0.786 inch and tangential rectilinear
`segments of 0.168 inch in length and which cross sec- 40
`tion extends throughout the length thereof. The total
`height of the cross section is 0.138 inch.
`The strip is then coated with a primer paint which is
`baked, and the strip is flattened by backbending and
`imprinted with the indicia in repeating patterns in ac- 45
`cordance with the desired lengths thereof. Preferably,
`the imprinted blade is then laminated in a polyethylene
`terephthalate film.
`The printed strip is then passed through a cutoff
`station where the precise lengths are severed and at 50
`which the intermediate portion of the severed length is
`simultaneously cold formed into the desired cross sec(cid:173)
`tion. This forming is performed in two steps in a press
`brake die which further forms the portion commencing
`at 42 inches from the 0 inch point of the blade and 55
`ending at 116 inches, and which uses a cooperating
`mandrel with tapered ends to effect a 2-inch transition
`from the original cross section to the new cross section
`(i.e., 42-44 inches and 114-116 inches). The cut off
`length is first further formed in one stroke along one 60
`side of the center line, and then along the other side of
`the center line in the second stroke, to produce a cross
`section in the intermediate portion where the.radius of
`the arcuate segment is 0.459 inch and the height is 0.226
`inch; the length. of the rectilinear segments is un- 65
`changed. Following this cold forming step to augment
`the curve in the intermediate section, the cut off lel)gth
`is stress relieved by front bending it about a roll and
`
`APEX TOOL GROUP, LLC - EX. 1008-007
`
`

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`4,429,462
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`9
`portion adjacent one end thereof with a depth H1 and a
`radius R1, a second portion extending from said first
`portion with a depth Hz and a radius Rz, and a third
`portion extending from said second portion to adjacent
`the other end thereof with a depth H3 and a radius R3,
`said second portion having a depth Hz greater than the
`depth H1 and H3 of said first and third portions and a
`radius R2less than the radii R1 and R3 of said first and
`third portions, said second portion extending for a por(cid:173)
`tion of the length of said blade which includes the nor(cid:173)
`mal breakpoint for a blade of said width and of a uni(cid:173)
`form cross section corresponding to the depth H1 and
`radius R1 of said first portion and which extends beyond
`said normal breakpoint towards said other end of said
`blade to provide greater standout length, the radius R2 15
`of said arcuate segment of said second portion decreas(cid:173)
`ing in length, and the depth H2 increasing, from said
`first portion towards said third portion of said blade.
`7. The coilable rule blade of claim 6 wherein the
`decrease in radius R2 and increase in depth Hz in said 20
`second portion are at a substantially uniform rate over
`substantially the entire length of said second portion.
`8. The coilable rule blade of claim 6 wherein the
`radius R2 of said second portion increases and the depth
`H2 decreases, at a rapid rate adjacent said third portion.
`9. The coilable rule blade of claim 1 wherein said
`blade has a terminal portion adjacent said