Strap cutting tool

A heavy-duty industrial tool has a working jaw mechanism operated by a pair of handles that are squeezed together. The upper handle has a main non-metallic handle member to whose sides are fastened a pair of stamped metal side members. These side members are in-laid into recesses in the sides of the non-metallic member to form a gripping portion. Forwardly of the gripping portion, the widths of the metallic members increase to form a throat within which the lower handle is pivotally mounted. The lower handle contains a stack of laminations, including a cutting blade that is forward of the pivot to form the upper jaw of the tool. The lower jaw is an anvil member that joins to flanges of the metal side members of the upper handle. When the tool is used to cut tensioned strapping, a resilient metal bracket attached to the blade presses the strapping against the anvil on opposite sides of the blade and deforms to absorb energy that is released by the strapping upon severing.

BACKGROUND AND SUMMARY OF THE INVENTION 
This invention relates generally to a strap cutting tool of the type used 
to cut tensioned strapping. In some respects, this invention is an 
improvement upon the strap cutting tool disclosed in the Applicant's prior 
Pat. No. 4,644,646 issued Feb. 24, 1987. In other respects, principles of 
the invention may be applied to similar types of tools that have a working 
mechanism operated by a pair of handles which are squeezed together. 
Problems related to the cutting of tensioned strapping are described in the 
aforementioned patent. The strap cutting tool disclosed in that patent 
comprises energy absorbing structures at lateral sides of the cutting 
mechanism which absorb energy released from the tensioned strapping upon 
severing. The energy absorbing elements prevent uncontrolled whipping of 
the severed ends of the strapping from the tool by means of their 
strategic configuration and arrangement on the tool. The disclosed energy 
absorbing structures are elastomeric bodies disposed on laterally opposite 
sides of the cutting mechanism and mounted on the cutting blade by a 
laterally extending support member attached to the top of the blade. An 
anvil portion of the tool underlies the energy absorbing structures and 
contains a centrally disposed slot having an edge with which the cutting 
edge of the blade coacts to sever strapping when the strapping is disposed 
between the anvil and the blade, and the tool handles are squeezed 
together. The energy absorbing structures forcefully hold the strapping 
against the anvil, compressing in the process, while retaining columnar 
stability in the direction of force application to the strapping. Upon 
severing, the energy that has been stored in the tensioned strapping is 
absorbed into the energy absorbing structures by their laterally yielding 
while they continue to forcefully hold the severed ends of the strapping 
against the anvil. In this way, the uncontrolled release of energy in the 
strapping upon severing is avoided. 
One aspect of the present invention relates to improvements in the energy 
absorbing structures for a strap cutting tool of the type that is 
disclosed in the aforementioned patent. 
While use of elastomeric elements as described in that patent still 
continue to be preferred, it has been found possible to fabricate energy 
absorbing structures of suitable resilient metals, such as spring steel, 
that are formed into particular configurations. Several configurations are 
specifically disclosed for purposes of explaining principles of this 
aspect of the present invention. 
Other principles of this invention relate to improvements in the 
fabrication of the tool, and these principles are applicable to various 
forms of pliers-type tools in addition to the disclosed strap cutting 
tool. 
The tool of Pat. No. 4,644,646 comprises a pair of members pivotally 
connected together about a pivot. Each member comprises a handle portion 
and a jaw portion. One member has a lower jaw portion and an associated 
upper handle portion; the other, an upper jaw portion and an associated 
lower handle portion. As the handle portions are squeezed together, the 
resultant action about the pivot results in the jaw portions being closed 
together to perform the cutting operation. Such a construction 
contemplates the two members being fabricated as metal forgings. Forging 
is a process that produces a strong part, but for mass production 
purposes, it may be too slow to be economical because forgings require 
subsequent costly machining operations. 
Accordingly, the present invention also relates to a novel and unique 
construction which is particularly well-suited for economical mass 
production fabrication of a heavy duty industrial pliers-type tool, such 
as embodied in the disclosed strap cutter. Moreover, these principles 
allow for the fabrication of a tool which is: esthetically pleasing in 
design; ergonomic; and functional. Novel features reside in the 
construction of the handles, the anvil and the blade and in the manner of 
assembly of the several parts. 
The foregoing, along with additional features, advantages and benefits of 
the invention, will be seen in the ensuing description and claims which 
are accompanied by drawings. The drawings disclose a preferred embodiment 
of the invention according to the best mode contemplated at the present 
time in carrying out the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIGS. 1 and 2 illustrate a strap cutting tool 20 embodying principles of 
the present invention. FIGS. 3-11 illustrate additional details. 
The strap cutting tool is a pliers-type device comprising two assemblies 22 
and 24 that are pivotally connected together about a pivot 26. Each 
assembly 22, 24, comprises a corresponding handle portion 22H, 24H and a 
corresponding jaw portion 22J, 24J. Handle portion 22H is considered the 
upper handle while handle portion 24H is considered the lower handle. Jaw 
portion 24J is considered the upper jaw while jaw portion 22J is 
considered the lower jaw. The solid line position illustrated in FIG. 1 
shows the jaws open. 
When the handles are grasped and squeezed together, such as in the manner 
portrayed by the arrow 28 representing relative movement of the lower 
handle toward the upper handle, the two jaws are urged together about 
pivot 26. Such action will serve to sever a piece of metal strapping (not 
shown) that is placed in the area designated by the numeral 30 in FIG. 1. 
Assembly 22H comprises a pair of metal side members 32, 34, a non-metallic 
handle member 36, and a metal anvil 38. Members 32, 34 and 36 are 
generally elongate and serve to form the entirety of upper handle 22H. 
Each of the side members 32, 34 may be considered to comprise two 
portions: one, a flat side portion 32S, 34S, respectively, that is 
disposed flat against a corresponding lateral side of handle member 36; 
and two, a flat flange portion 32F, 34F, respectively, (see FIGS. 3 and 5) 
that provides for the attachment of anvil 38. Each side portion 32S, 34S 
is planar; so are the corresponding flange portions 32F, 34F, 
respectively, but each is disposed outwardly at a right angle to the 
corresponding side portion 32S, 34S, and is connected by a curved bend to 
the corresponding side portion. 
In plan, anvil 38 has a generally rectangular shape although the two 
leading, or forward, corners have tapers 40 and 42, respectively. The 
trailing, or rearward, corners are provided with rectangular recesses 44, 
46, but only in the lower surface of the anvil. These recesses 44 and 46 
have areas and depths corresponding essentially to the areas and thickness 
of flanges 32F and 34F. A rectangular slot 48 in the anvil allows that 
portion of upper handle 22H that is immediately contiguous flanges 32F and 
34F to fit between the two sides of the anvil that contain the respective 
recesses 44, 46. The two flanges fit in a generally flush manner in the 
two recesses, and secure attachment is accomplished by any suitable means, 
such as screws or rivets 50, two per flange, which pass through aligned 
holes in the flanges and the corresponding portions of the anvil. 
Handle member 36 is not fully coextensive in length with the side portions 
32S, 34S in the direction toward pivot 26 and anvil 38. Member 36 
terminates in an angled surface designated by the reference numeral 51 in 
FIG. 1. Accordingly, a throat area 52 is defined between members 32 and 34 
immediately contiguous flanges 32F, 34F and anvil 38. Assembly 24 passes 
through this throat area 52, and the pivot 26 between the two assemblies 
22 and 24 is also provided in this area. 
Assembly 24 comprises a handle member 54 and a stack of laminations, 56 
generally. There are three laminations in stack 56, one of which is a 
blade element 58, shown by itself in FIG. 10, and the remaining two of 
which, elements 60, 62, are identical in shape as portrayed in FIG. 11. 
Blade element 58 possesses a convexly curved cutting edge 64. The shapes 
of elements 60, 62 are congruent with that of blade element 58 except 
along cutting edge 64 where the elements 60 and 62 are relieved to provide 
clearance for edge 64. Registering hole patterns 66 are provided in 
elements 58, 60 and 62, and the three elements are secured together in 
lamination by rivets 68, 69 at the two registered holes forward of pivot 
26 and by rivets 70 and 72 which pass not only through the two registered 
holes rearward of pivot 26 but also through registering holes in the sides 
of handle member 54 thereby securely joining the latter to the stack 56. 
It can be seen in FIG. 8 that handle member 54 has a generally U-shaped 
transverse cross section whose throat is dimensioned to fit closely onto 
the end portion of the laminated elements that points away from pivot 26. 
With the organization and arrangement of the two elements 60 and 62 
relative to element 58, the cutting edge 64 is allowed to protrude free 
and clear for effective action in cooperation with the anvil in cutting 
strapping placed between the two jaws 24J, 22J that are formed by the 
lamination stack and the anvil. Near the distal end of handle member 54 is 
a small hole 73 that allows the tool to be hung on a hook or a nail when 
not in use. 
Pivot 26 comprises a fastening mechanism, 74 generally, that passes through 
registering holes 75 in stack 56 and the side portions 32S, 34S of members 
32, 34. The fastening mechanism comprises a headed screw 76 with a washer 
78 disposed between the head of screw 76 and one of the side members 32, 
34. The shank of screw 76 passes through the registering holes to protrude 
from the opposite side. A washer 80 is fitted over the protruding end of 
the screw shank, and a prevailing torque look nut 82 is threaded onto the 
screw shank and tightened to secure the two assemblies 22, 24 in pivotal 
mounting. The nature of the fastening action of mechanism 74 is such that 
the fastening mechanism does not rotate with respect to assembly 22 when 
the handles are operated; rather, assembly 24 rotates on the screw shank, 
and thus all relative movement about the screw shank takes place within 
the confines of throat area 52. 
Anvil 38 contains a channel-shaped groove 84 that extends forwardly from 
slot 48. The groove's width is equal to that of slot 48 minus essentially 
the thickness of member 32. The reduction in width is on the left side of 
groove 84 as viewed in FIG. 4 so that the left edge 86 of groove 84 as 
seen in that FIG. is juxtaposed for coaction with edge 64 of blade 58 for 
cutting strapping. In addition to the tapered corners 40, 42, the anvil 
has its top surface provided with a rather gradual taper 88 that is 
generally coextensive with the line of action of edge 64 along groove 84. 
This gradual taper merges into an increased taper 90 at the forward end of 
the anvil, and its purpose is to facilitate lodging of the anvil beneath a 
tensioned strap that is to be severed. Advantageously, the anvil is a 
one-piece element that can be manufactured by conventional procedures and 
also easily machined to provide a satisfactory sharpness for edge 86. 
Upper handle 22H comprises a gripping portion, 88 generally. This gripping 
portion is adapted for spanning the palm of the hand when the tool is 
grasped and the handles are squeezed together. For this purpose, the 
gripping portion has a slightly convexly curved shape as viewed in FIG. 1, 
and as perhaps best seen in FIG. 6, the exposed top surface of handle 
member 36 is rounded (numeral 90) while the side members 32 and 34 are 
inlaid into complementary contoured recesses 92, 94 in the sides of member 
36 so that side members 32, 34 are substantially flush with handle member 
36. 
Members 32, 34, 36 are securely joined in assembly by a series of four 
rivets 96 arranged as shown at increments along the length of the handle. 
At the extreme distal end of gripping portion 88 in the direction away 
from pivot 26, the transversely rounded upper surface of member 36 is also 
rounded in the distal sense (numeral 98) to extend downwardly in covering 
relation (numeral 100) to the distal ends of side members 32, 34. Member 
36 is proportioned relative to side members 32, 34 along gripping portion 
88 such that when the handles ar grasped and squeezed together, the 
squeezing force that is exerted by the palm of the hand on the upper 
handle member is distributed essentially on the rounded top surface of 
handle member 36. 
Moreover, the gripping portion 88 is configured to have a raised stop 102 
at the end thereof that is toward pivot 26. This stop is adapted to fit in 
the area between the base of the thumb and that of the index finger to 
resist any tendency of the user's hand to slide forwardly along the 
handles as they are being squeezed. 
A pair of energy absorbing structures 104, 106 are disposed to each lateral 
side of blade 58. These structures are attached to the ends of a laterally 
extending metal support plate 108 which is attached centrally to the top 
side of the stack of laminations forwardly of pivot 26. Screws 110 pass 
through clearance holes in support plate 108 and into tapped holes in the 
laminated stack. 
The energy absorbing structures are in the form of elastomeric elements of 
the type described in patent 4,644,646. As such, when tensioned strapping 
is placed between the open jaws and the handles are squeezed together, 
elements 104, 106 press the strapping against the underlying anvil to each 
side of blade 58 as the blade is severing the strapping. As the severing 
is being completed, the energy of tension that has been stored in the 
strapping is absorbed by elements 104, 106, yielding laterally to absorb 
the energy while still holding the severed ends of the strapping 
forcefully against the anvil. In this way, the undercontrolled whipping of 
the severed ends from the tool is avoided. Further description and details 
of the elastomeric elements may be had by reference to patent 4,644,646. 
The strap cutting tool 20 is advantageous for mass production fabrication 
because many of its parts are metal stampings which can be economically 
and rapidly produced. The stamped metal parts are the side members 32, 34, 
the handle member 54, the lamination members 58, 60, 62, and the support 
bracket 108. Such parts have precise thicknesses, are stamped to finished 
shapes, and require minimal secondary operations, if at all. For one 
example, the stamping of the metal side members 32, 34 provides their 
finished shape, including the formation of the required holes and the 
outward turning of the flange portions 32F, 34F. For another example, a 
single die can be used to fabricate elements 58, 60, 62 even though 
elements 60, 62 have a different shape along the edge that is next to the 
blade edge 64 of element 58; this is done by designing the basic die for 
stamping element 58, and then whenever elements 60, 62 are to be stamped, 
a suitable insert is placed into the basic die. Since element 58 and anvil 
38 are the sole parts that have cutting edges, only they need be made of 
harder, and more costly, intermediate to high carbon steel; other metal 
parts, such as elements 60, 62 and side member 32, 34 can be made of less 
hard and less costly steel. 
While the anvil is a one-piece member that can be economically fabricated 
by conventional techniques, investment casting of this part provides 
special benefits, and it is the preferred procedure for making the anvil. 
The anvil can be fabricated to the shape that has been illustrated and 
described, and then all that need be done is to finish the cutting edge 86 
to the desired sharpness. Note that investment casting provides for the 
rounding off of the corner tapers 40, 42 into the tapered surface 90; this 
feature facilitates the insertion of the anvil beneath tensioned strapping 
because rounding promotes a more gradual flexing of the strapping where 
the rounding contacts the strapping as the anvil is being inserted beneath 
the strapping. 
The various fasteners, including those used for the pivot 26, are also 
conventional parts. 
Although the tool is fabricated of a number of stamped metal parts, there 
are a number of inventive features in the organization and arrangement 
that lead to a construction well-suited for a heavy-duty industrial-type 
hand tool. 
The pliers-type action of the tool imposes bending loads in the handles and 
jaws. The members take advantage of the high tensile strength of steel in 
resisting these loads. The laminated stack 56 and the anvil 38 possess 
high strength because they are steel and they have significant thickness. 
Although they are thinner than stack 56 and anvil 38, the stamped side 
members 32, 34 are arranged to have a high moment of inertia in the 
direction of the bending loads. Forwardly from the forward end of gripping 
portion 88, where the closing forces are amplified, the width of members 
32, 34 progressively increases. Although their widths are less along the 
gripping portion, side members 32, 34 have a rigid cooperative coaction 
with member 36, as received in contoured recesses 92, 94 and joined to 
member 36, especially during bending, along the upper edge of each side 
member which is disposed against the corresponding edge of the 
corresponding recess 92, 94. Two rivets 96 attach the side members to the 
handle member along gripping portion 88 while the two remaining forward 
rivets 96 resist the bending moment couple that is transmitted along the 
handle during strap cutting. 
The tool further resists bending action during cutting by the manner in 
which flanges 32F, 34F are arranged and attached to anvil 38. During 
strapping cutting, the bending moments in the tool tend to bend the fronts 
of flanges 32F, 34F upwardly. By placing these flanges underneath the 
anvil, the peak forces on the fasteners 50 at each flange are reduced from 
what would be the case if the flanges were on top of the anvil, 
particularly for the front fasteners, both of which are nearer pivot 26, 
and especially the front fastener that is nearer blade 58 where the 
bending moment is greatest. 
Not only is flange 32F in full abutment with the anvil, but moreover, the 
portion of side 32S that is immediately contiguous flange 32F is 
essentially in full abutment with the side of groove 84, a further 
strengthening feature of the tool. This two-sided abutment of member 32 
with anvil 38 is achieved by incorporating a small chamfer 111 along the 
lower edge of the side of groove 84 to accommodate the curved bend that 
joins flange 32F and side 32S in member 32. 
Member 36 is preferably a suitable non-metallic structural material that 
can be mass produced by conventional techniques such as molding. A 
preferred material is glass-filled or glass-reinforced nylon. Such a 
material is structurally very strong, dimensionally stable, and yet can be 
formed with comfortable rounded contours particularly in the area of 
gripping portion 88. Assembly of the various component parts can be 
expeditiously accomplished using conventional assembly techniques and 
procedures. Therefore, a tool fabricated in accordance with the present 
invention is in certain respects more cost-effective for mass production 
than the tool that is the subject of the Applicant's prior Pat. No. 
4,644,646. The construction of the handles is a feature which can be used 
in various forms of pliers-type tools other than the illustrated strap 
cutting tool. 
Further features of the invention more specific to a strap cutting tool are 
illustrated in FIGS. 12 through 17. FIGS. 12-14 illustrate a second 
embodiment of energy absorbing structures in the form of a one-piece 
spring steel part 112. Part 112 is intended to be substituted for the 
energy absorbing structures 104, 106 and the support plate 108 in tool 20. 
Part 112 comprises a top laterally extending portion 114 with a pair of 
holes 116 for use in attachment by screws 110 to the top of stack 56. The 
part further comprises laterally spaced apart leaf sections 118, 120 that 
correspond to the resilient elastomeric elements 104, 106. Each leaf 
comprises a pad 122, 124 that is spaced vertically below and disposed 
generally parallel to section 114. A curved bend 126, 128 integrally joins 
the forward, or leading, portion of each pad 122, 124 with a corresponding 
edge portion of section 114. Curved upturned lips 130, 132 are provided 
along the edge portions of the two pads 122, 124 that face each other 
across the opening between the pads that is provided for the cutting 
mechanism. Additionally, the trailing edge of each pad is provided with an 
upturned lip 134, 136. 
With part 112 securely attached to the tool, it will function to prevent 
the uncontrolled whipping of the ends of a severed strap from the tool by 
absorbing a substantial portion of the energy that is released by the 
strap upon severing. As the tool is operated to sever the strapping, pads 
122, 124 are pressed against the strapping to each side of the line of 
severing. As the jaws close further, the force pressing on the strapping 
increases because it is necessary for part 112 to deflect as the jaws are 
being closed. The exact manner of deflection will depend upon the 
particular geometry, thickness, and spring characteristics of part 112. In 
general, the deflection during jaw closing and before completion of 
severing will take place in the curved sections 126, 128 and in bending of 
section 112 about its point of attachment to the stack 56. During this 
time, the pad continues to press the strapping forcefully downwardly 
against the underlying anvil still constraining the strapping against 
movement on the anvil. 
As the severing is completed, the energy that has been stored in the 
tensioned strapping is released. Because the force of part 112 still 
continues pressing the severed ends of the strapping against the anvil, a 
substantial portion of the released energy is absorbed by a further 
deflection or deformation in part 112, due to slight lateral outward 
displacement of the pads in response to the laterally outward forces in 
the severed ends of the strapping. The particular deformation once again 
is a function of the particular shape, thickness, spring characteristics, 
etc. of part 112. In this way, the uncontrolled whipping of the severed 
ends of the strapping from the tool is resisted. 
The lips 130, 132, 134, 136 serve two purposes: one, they stiffen the pads 
122, 124 so that they tend to remain flat when pressing the strapping 
against the anvil; two, they also serve to facilitate removal of strapping 
from the tool thereby minimizing the tendency for an edge of the strapping 
to hang up on an edge of the pad. 
FIG. 15 shows another modified embodiment 138 for the energy absorbing 
structures which is similar to part 112. Like reference numerals are used 
to designate corresponding parts in both part 112 and part 138. The 
principal difference between part 112 and part 138 is that in part 138 the 
curved sections 126, 128 join the lateral side edge portions of the top 
section 114 with the outboard lateral edge portions of the pad. Part 138 
resiliently deforms during the strap cutting operation to press the 
strapping against the underlying anvil and then to absorb a substantial 
portion of the tensioned energy that is released from the strapping upon 
severing. 
FIG. 16 illustrates a still further modified form 140 based upon a 
modification of part 138. According to this modification, notches 142 are 
provided in opposite sides of the central region of the curved sections 
126, 128, thereby changing the deformation characteristics. 
In FIG. 17 a further modified part 144 is shown. This part is similar to 
part 138 except that the curved sections are bowed into a somewhat larger 
shape once again changing the deflection and deformation characteristics. 
FIG. 18 illustrates the incorporation of an optional feature into tool 20. 
This feature is a return spring 146 which provides a reopening force 
aiding reopening of the jaws after the tool has been operated to sever a 
piece of strapping. The spring is disposed in spaced relation to pivot 26 
and acts between the two handles. Anchoring of the end of the spring to 
lower handle 24H is by means of a spring seat formation 148 in the middle 
of the three laminations of stack 56. The opposite end of the spring is 
anchored on the upper handle 22H by means of a spring seat 150 integrally 
formed in handle member 36. 
The full open position of jaws 22J, 24J is defined by abutment of the rear 
edge of support plate 108 with the foreward edges of side members 32, 34. 
This is indicated generally by the numeral 152 in FIG. 1. By making the 
holes in support plate 108 slightly oversized in comparison to the shanks 
of screws 110, the position of plate 108 may be set to a desired position 
of adjustment before screws 110 are tightened so that the limit of opening 
occurs for a certain predetermined amount of opening of jaw 24J relative 
to jaw 22J. The shortest distance across this opening occurs just in front 
of throat 52 and is set, via the aforedescribed adjustment of support 
plate 108 to accommodate the maximum thickness of strapping that is to be 
cut. In this way, the actual cutting action on a piece of strapping that 
is fully inserted into the fully opened jaws will occur as early as 
possible during the operation of the handles where greater manual forces 
are typically generated. The maximum degree of closing of the jaws is 
established by abutment of the chamfered surfaces 154 of handle member 54 
with the lower edges of side members 32, 34, as indicated by the reference 
numeral 156 in FIG. 1. 
If necessary, the tool can be disassembled for resharpening either or both 
edges 64 and 86. Although the cutting blade element 58 has been described 
as being riveted to the other two elements 60, 62, it is contemplated that 
removable fasteners such as screws could be used instead. In this way, the 
blade element itself could be removed and resharpened or alternatively 
replaced by a fresh blade element. 
Still further, it is contemplated that the cutting blade could be a 
replaceable insert 158 such as the one illustrated in FIG. 19. This 
embodiment shows the blade shape generally similar to the shape of jaw 24J 
that appears in FIG. 1. The stack 56 still has the lamination elements 60 
and 62 (although these two could conceivably be one piece). An additional 
piece, in cooperation with the insert, have a combined shape like the 
blade shape shown in FIG. 10. Thus, there is still a lamination that 
pivotally mounts in the same manner previously described for assembly 24. 
However, the replaceable inserted blade removably fastens to this stack 
alongside the forward portions of the stack constituting the upper jaw 
24J. 
A preferred manner of attachment comprises a pair of spaced apart hardened 
pins 160 that are fitted to the two forward holes in the two members 60, 
62 and which project to fit into registering holes 162 in the inserted 
blade. There is one additional hole 164 that provides for use of a screw 
(not shown) to removably attach the insert to the stack. The use of close 
fitting hardened pins serves to react the cutting loads imposed during 
usage of the cutting tool. The fastener screw does not react nearly the 
same magnitude of loads but rather serves to keep the blade insert forced 
against the stack. 
The foregoing description has disclosed and illustrated improvements in a 
strap cutting tool. Certain improvements are specific to the strap cutting 
tool while others can be used in various pliers-type tools, including a 
strap cutting tool. While a preferred embodiment has been disclosed, it 
will be appreciated that principles are applicable to other embodiments.