Swing saw for cutting metal conduit

A hand tool comprising elements for clamping a conduit or cable to be cut, a saw blade supporting assembly pivotally connected to the clamping elements, in a manner to guide the saw in its desired cutting path, and means for causing sawing movement of the saw blade, the saw blade supporting assembly and the clamping elements being so juxtaposed that they can be gripped by one hand of the tool operator to cause both gripping of the work and advancement of the saw blade in its cutting position; the other hand of the operator being available to effect cutting movement of the saw blade.

This invention relates to a swing saw in the nature of a hand tool for 
cutting elongated materials such as tubular metal conduit or cable, and 
particularly a flexible conduit comprising a metal tube covered with a 
plastic jacket. 
BACKGROUND OF THE INVENTION 
Plastic clad metal conduit of the type referred to is commonly used 
outdoors in connection with commercial installations such as air 
conditioning apparatus or indoors for supplying hydraulic or pneumatic 
power to a point of utilization. The ends of the conduit sections are 
normally cut square and used with special fittings with seals which 
provide an assembly impervious to fluids such as water or oil. 
Such conduit is usually cut with a hacksaw, but the flexibility of the 
conduit makes this somewhat difficult. The operation may be facilitated by 
a device utilizing a small miter box to guide the hacksaw, but 
considerable effort is still required to hold the conduit and obtain a 
clean cut. 
OBJECTS OF THE INVENTION 
It is an object of the present invention to provide a hand tool which has 
both conduit-holding means and conduit cutting means. 
It is a further object of the invention to provide such a tool wherein the 
cutting means is a hacksaw and the holding means is an alligator-type 
clamp. 
It is another object of the invention to provide a tool wherein the hacksaw 
can be operated with a mechanical advantage to cut the work rapidly and 
accurately in a plane perpendicular to the length of the conduit. 
It is a still further object of the invention to provide a hand tool 
wherein the firm grip of one hand of the operator serves both to maintain 
clamping pressure on the work and to maintain downward cutting pressure on 
the saw. 
It is yet another object of the invention to provide a tool wherein certain 
parts can be folded to relatively retracted positions, and held there, for 
convenience in carrying and/or storing the tool. 
It is also an object of the invention to provide certain improvements in 
the form, construction and arrangement of the several parts of the tool 
whereby the above-named and other objects may effectively be attained. 
The invention accordingly comprises the features of construction, 
combination of elements, and arrangement of parts which will be 
exemplified in the construction hereinafter set forth, and the scope of 
the invention will be indicated in the claims. 
SUMMARY OF THE INVENTION 
The tool comprises an elongated main body portion adapted to be grasped by 
the operator's hand, an elongated saw carrier pivotally connected to the 
body portion at their rear ends, a saw blade connected to the carrier by 
parallel links (one of which is extended to constitute an operating 
handle), a clamping lever pivotally mounted adjacent the forward end of 
the body portion and a clamp carrier integral with the body portion and 
extending downwardly at an angle from said forward end of the body 
portion. The active elements of the work clamp are constituted by a fixed 
jaw adjustably mounted on the clamp carrier, and a serrated jaw surface on 
the clamping lever, facing the fixed jaw. The parts are arranged and 
proportioned so that work held firmly in the clamp lies in the cutting 
path of the saw blade when the saw carrier is depressed, and the blade can 
be reciprocated by actuation of the operating handle to effect cutting of 
the work.

DETAILED DESCRIPTION 
Referring to the drawings, the body portion 10 is constituted by a pair of 
elongated side plates 11, held in parallel spaced relation by screws 12, 
12' which pass through the bores of tubular spacers 13, 13', there being 
two such points of connection adjacent the rear end of the body portion 
and one near the forward end, as clearly appears in FIG. 1. 
The saw carrier 15 comprises a handle portion 16 and a bow portion 17 
integral with the handle, the handle portion being shorter than the body 
portion 10 and pivotally mounted thereon by means of the upper rear spacer 
13'. The bow portion 17 projects forwardly from the handle portion, in a 
flat arch, a distance sufficient to provide a "parallelogram" mounting for 
the blade support links 18 and 19 carrying a hacksaw-type blade 20. The 
link 18 is pivotally mounted at a point 21 near the base of the bow 
portion and the link 19 is mounted at the forward end of the bow portion 
at the point 22, this forward link having an upward extension 19' on which 
is mounted a foldable handle 25, described below. The saw carrier assembly 
is biased toward the raised position shown in FIG. 1 by a spring 26 which 
rests on a short "floor" piece 27 extending between the plates 11 near 
their rear ends. 
In order to maintain the saw blade under tension, as is customary in 
hack-saw construction, the link 18 can be provided with an upward 
extension 18', as shown in FIG. 5 which is connected by a tensioning rod 
23 with turnbuckle 24, to a pivot pin 23' on the extension 19' of the link 
19, the tensioning assembly 23, 24 forming, with the saw blade and the 
links, a substantially perfect parallelogram. 
The conduit clamp 30 is constituted by elongated clamp plates 31, 
preferably integral with side plates 11 and projecting downwardly and 
forwardly from the forward ends of the side plates. The clamp plates are 
provided with elongated slots 32 and a lower clamp jaw 33 is slidably 
mounted between the plates, being held in any desired adjusted position by 
means of a bolt 34, FIG. 4, passing through a hole in the clamp jaw, 
through the slots 32 and carrying the wing nut 35 adjacent its free end. 
The sides of the clamp jaw are rabbeted as shown at 33' to form 
rectangular grooves which receive the plates 31 with a close sliding fit, 
so that the jaw maintains a constant angle with said plates in every 
adjusted position. The working face 36 of the clamp jaw 33 is serrated and 
it is deeply slotted as shown in FIG. 4. The clamp is completed by the 
clamping lever 37, having a handle portion 38 (channel-shaped in 
cross-section, FIG. 2) and a pair of spaced jaw portions 39 each having a 
serrated edge 40 facing the clamp jaw face 36. The lever 37 is pivotally 
mounted on the walls of the body portion by means of separate pivots 41, 
one on each side to leave clear the space between side plates 11; the 
pivots 41 may be screws or rivets and the lever is biased toward a clamp 
open position by the leaf spring 42 bearing against the forward spacer 13. 
The links 18 and 19 may conveniently be rectangular in cross-section and 
slotted at their lower ends to provide freedom of movement for the saw 
blade mounted therein. A releasable blade attachment device is shown at 
the right of FIG. 10 wherein the saw blade end (not shown) fits freely in 
the slot 45 with the pin 46 passing through the hole normally provided at 
each end of a hacksaw blade. The pin 46 rests slidably in the bore 47 
which traverses the link 19 (or 18) and is held in blade-locking position 
by the spring 48 within a protective cap 49. To retract the pin 46 a nail 
or other small pointed device may be inserted in the open end of the bore 
47, causing compression of the spring 48; with the pin pushed back a 
hacksaw blade can readily be inserted or removed. The foldable handle 25, 
as shown in FIG. 6, has a clevis end 51 pivotally mounted by the pin 52 
near the upper end of the link extension 19', which link end is also 
provided with a tapered axial socket 53. The handle body 54 is hollow and 
houses a plunger 55, the tapered lower end of which is urged toward 
engagement in socket 53 by the spring 56. The plunger passes freely 
through the bore of a plug 57 secured in the end of the handle, and the 
outer end of the plunger is provided with a button 58 by means of which 
the plunger can be moved, against the urging of the spring 56, to free its 
tapered end from the socket 53 when it is desired to fold the handle, 
e.g., toward the position shown in broken lines in FIG. 1. 
The folding of the tool is also facilitated by the provision of a latch or 
hook 59 which can be hooked over the projecting end 21' of the pivot 21 to 
hold the saw and clamp assemblies in their most compact over-all 
positions; the handle 25 being also folded back, of course. 
As a desirable additional feature, the de-burring device shown in FIG. 7 
may be added, for instance, at the rear end of the body portion 60, this 
device comprising a flat metal plate 61 the square end of which is riveted 
to the side of body portion 11 while the end having a 90.degree. V-shaped 
notch 62 projects rearwardly. A separate flat metal plate 63 having a 
90.degree. pointed end 64 and a longitudinal slot 65 is adjustably secured 
to the plate 61 by means of a wing nut and bolt 66. The edges of the notch 
and of the point are sharpened sufficiently to remove burrs from the cut 
ends of conduit sections when the ends are pressed against the said edges, 
at their intersection, and the conduit section manually rotated. 
Adjustment for different diameters can be effected by sliding the plate 63 
relative to the plate 61. 
In the alternative form of tool shown in FIG. 11 the band saw assembly of 
FIG. 1 is replaced by an electric power operated saber-saw comprising the 
saw blade 70 projecting from one end of the elongated housing 71 which 
contains a motor and is held by the hand grip 72 containing a switch 73. 
The work holding assembly 74 is similar, in its clamping elements, to the 
corresponding parts described above. The body portion is constituted by 
side plates 75 pivotally mounted at points 76 adjacent their rear ends on 
a strap 77 encircling the housing 71. At their work-supporting ends the 
plates 75 extend downwardly and forwardly, like the clamp plates 31, to 
carry a lower clamp jaw 78, like the jaw 33, with the same means for 
adjustment. The clamping lever 79, with jaw 80, is pivoted at 81 on the 
side plates 75 so that the operator can keep the jaw faces firmly engaged 
with the work while the same manual gripping force urges the work holding 
assembly, on pivot point 76, toward the cutting position as indicated by 
the arrow. A leaf spring 83 on the rear of the lever 79 serves the same 
function as spring 42 in FIG. 1. 
Since the operator may, for any reason, wish to interrupt the sawing 
operation before a cut has been completed, means may be provided for 
holding the clamp jaws in closed position on the work. Such a means is 
shown in FIGS. 8 and 9 as comprising a ratchet device 90 pivotally mounted 
at 91 adjacent the rear end of the clamping lever 37 and provided with 
ratchet teeth 92 in a position to engage the forward edge of the floor 
piece 27. The ratchet is biased toward locking position by a spring 93 
between the lever 37 and a forward extension 94 and unlocking is effected 
by upward pressure on the rearwardly extending tab 95. 
The alternative form of saw blade shown in FIG. 6 may be resorted to in 
order to provide greater rigidity and more accurate side guidance, or a 
truly square cut. This blade 96 has a convex upper edge 97 so that the 
middle portion has much more material--and stiffness--without any increase 
in blade thickness. 
In the operation of the tool shown in FIGS. 1 to 6, the position of the 
lower jaw 33 is adjusted, by loosening the wing nut 35, sliding the jaw 
along the clamp plates 31 as required by the outside diameter of the 
conduit to be cut and tightening the wing nut, to hold the lower jaw in a 
position such that the conduit can be easily inserted between the face of 
jaw 33 and the jaw faces 40 on the jaws 39. With the saw handle 25 locked 
in its straight-out position (FIGS. 1 and 10) the operator grasps the tool 
with one hand gripping the body portion 10, the handle portion 16 of the 
saw carrier and the handle portion 38 of the clamping lever 37. The 
fulcrum point 41 of the lever 37 is close to the jaw 39, so that pressure 
on the handle 38 effects strong and positive gripping of the conduit 
between the jaws 33 and 39. The fulcrum point of the saw carrier 15 is at 
the screw 12' and spacer 13', so that the same gripping force which holds 
the conduit very firmly serves to urge the saw carrier downward in a 
relatively gentle and controllable manner. When the saw blade 20 has been 
brought into contact with the conduit, at the point where a cut is to be 
made, the saw is reciprocated by the use of the operator's other hand, 
grasping the handle 25 and moving it back and forth to cause sawing 
movement of the blade. Due to the linkage mounting of the saw blade the 
saw carrier 15 will oscillate vertically during each stroke, but short 
strokes are effective and the vertical oscillation can easily be 
accommodated by the resilience of the operator's grip on the handles. The 
angle of the saw teeth is preferably such that the cut material is removed 
primarily on the rearward (pulling) stroke of the handle. Since the jaw 
faces 40, 40 are widely spaced and the jaw face 36 is deeply slotted (FIG. 
4) the saw blade has a clear path to cut cleanly and completely through 
the work piece (conduit), while the latter is held firmly at spaced points 
on each side of the cut. 
While the clamp faces 36 and 40 are shown as being generally straight, in 
profile, and serrated or knurled, it will be understood that one or both 
faces could, if desired, be curved or V-shaped in profile. 
In the event that any slight burrs are formed on the inner or outer edges 
of the cut surface, they can be removed very readily by means of the 
device shown in FIG. 7, as noted above. If the work is a cable or the 
like, rather than a tube, the plate 63 can be removed and the outer edge 
smoothed in the same manner. 
In the operation of the alternative form of the tool, shown in FIG. 11, one 
hand of the operator grasps the reduced diameter forward portion 71' of 
the housing 71 in a grip which easily includes the clamping lever 79, 
urging the clamping lever into tight engagement with the work (conduit) 
and swinging the clamp assembly and work on pivot 76 toward the saw blade 
70. The other hand of the operator holds the hand grip (pistol grip) 72 
and presses the switch 73 to cause the motor to reciprocate the saw blade. 
In the operation of each embodiment, one hand is concerned only with 
gripping and feeding the work and the other hand is concerned only with 
actuation of the saw. 
It will thus be seen that the objects set forth above, among those made 
apparent from the preceding description, are efficiently attained and, 
since certain changes may be made in the above construction without 
departing from the spirit and scope of the invention, it is intended that 
all matter contained in the above description or shown in the accompanying 
drawings shall be interpreted as illustrative and not in a limiting sense.