Hand tools abstract
A safety device for hand tools includes a casing having a first
clasp secured to the casing for mounting to the tool. A second clasp
is mounted to a retractable cable connected to a constant tension
cable reel mounted within the casing: The cable is payed out of
and retracted into the bottom of the housing in its normal use position,
and the second clasp is attached to a fixed support or "lock
point" located below the normal working height of the tool.
In use, when the tool is held by a worker and the housing is upright,
a lock plate is disengaged from a ratchet plate fixed to the retractable
reel so the tool is freely moveable relative to the lock point and
easily maneuvered. If the tool is dropped, the reel retracts the
cable as the tool begins to fall. The device is inverted as it falls
below the lock point. As the device turns over, the lock plate shifts
under gravity, and the weight of the tool places the cable in tension
and tries to counter-rotate the hub, thus causing the lock plate
to rapidly engage the ratchet plate and lock the reel, preventing
further cable pay out and securing the tool before it strikes the
floor or ground.
Hand tools claims
1. A tether device for a tool comprising: a housing having a top
and a bottom in an upright position for normal use, an attachment
device secured to said top of said housing and adapted to be attached
to a tool; a shaft mounted in said housing; a retractable reel mounted
for rotation on said shaft, said reel including, a hub defining
a set of radially extending teeth; a constant tension spring having
a first end fixed to said shaft and a second end attached to said
hub; a cable having a first end attached to said hub and a second
end extending externally of said housing for attachment to a lock
point; a lock plate having at least one tooth adapted to engage
with said teeth of said hub and inhibit rotation of said hub when
engaged, said lock plate mounted within said housing for sliding
movement between a first disengagement position when said housing
is in an upright position in which said lock plate is free of said
hub and said hub is free to rotate about said shaft, and a second
position when said housing is inverted, to lockingly engage said
hub to prevent rotation thereof; said housing guiding said lock
plate between said disengagement and engagement positions, while
restraining said lock plate against rotation relative to said housing.
2. The device of claim 1 wherein said lock plate defines a plurality
of teeth for engaging said teeth of said hub, and said teeth of
said hub and said teeth of said lock plate are asymmetrical, wherein
when said device is in a generally upright position, said hub is
rotated in a direction to retract said cable and said teeth of said
hub may override said teeth of said lock plate thereby continuing
to retract said cable and shorten the length of said cable extended
externally of said housing; and wherein as said device is inverted,
the weight of said tool causes said hub to counter-rotate, thereby
causing said lock plate to rapidly lockingly engage said hub.
3. The device of claim 2 wherein said housing includes a first
and second housing sections enclosing said reel; one of said housing
sections defining a receptacle slidably receiving said lock plate
while restraining rotation of said lock plate relative to said housing.
4. The device of claim 3 wherein said shaft is mounted to said
first and second housing sections, one of said housing sections
engaging an end of said shaft to prevent rotation of said shaft.
5. The device of claim 1 wherein said hub include a plate, a cylindrical
wall fixed to said plate, and a set of teeth extending circumferentially
about said plate, said lock plate positioned to engage said circumferential
teeth in a first, locking position, said locking plate adapted for
movement between said locking position and an unlocking position.
6. For use in combination with a tool, a tether device comprising:
a mounted shaft in association with said tool; a retractable reel
mounted for rotation on said shaft, said reel including, a hub defining
a set of radially extending teeth; a constant tension spring having
a first end fixed to said shaft and a second end attached to said
hub; a cable having a first end attached to said hub and a second
distal end for attachment to a lock point; a lock plate having at
least one tooth adapted to engage with said teeth of said hub and
inhibit rotation of said hub when engaged, said lock plate mounted
for sliding movement between a first disengagement position device
in an upright position in which said lock plate is free of said
hub and said hub is free to rotate about said shaft, and a second
position when said device is inverted, to lockingly engage said
hub to prevent rotation thereof; and a receptacle for holding and
guiding said lock plate between said disengagement and engagement
Hand tools description
 This application claims benefit of the priority filing of
U.S. Provisional Application Ser. No. 60/647497 filed on Jan. 27
2005 for "SAFETY TETHER FOR HAND TOOLS".
FIELD OF THE INVENTION
 The present invention relates to a safety device for hand
tools; and more particularly, it relates to a safety device for
the type of hand tools typically used in the construction industry
and other applications in which a worker may use the tool at levels
above the shoulders of the user, and even at full arm's length above
the user's head. If the tool were to fall from such a height and
strike the floor, the impact could cause damage to the tool and/or
any object struck by it.
 Hand tools of the type with which the present invention
is concerned, include drills, electrically driven screw drivers,
reciprocating chisels and the like. Some of these tools may weigh
up to ten pounds; and they are used in a wide variety of work situations.
In some cases, the worker may be on a ladder and working at shoulder
level or above. In other cases, the worker may be on his feet and
operating the tool at a level near or above his head. Obviously,
the impact on a tool falling from a height of six feet or more,
and colliding with an industrial surface, such as concrete, can
cause severe damage to the tool. In cases where the worker is working
above a surface, such as marble or wood, the surface itself could
be damaged by a tool impact resulting from a fall at these heights.
Hand tools of this type, particularly those of industrial or professional
grade, are expensive to repair or replace. Moreover, such a fall,
if unchecked, could result in injury. Further, time is lost in locating
a replacement tool if the fallen tool is damaged to the point where
it cannot operate.
 It is thus desirable to provide some means for arresting
the fall of hand tools under normal use conditions such that the
tools are not damaged, personnel are protected from falling tools
over substantial vertical distances, and surrounding environments
are protected against damage; and it is desirable that this be done
without unduly restricting the maneuverability of the tool or constrain
the movements of the worker.
SUMMARY OF THE INVENTION
 The present invention provides a safety device in the form
of a tether for hand tools. The device includes a casing (which
could be a casing of the tool itself since the device could be incorporated
into the tool itself) which houses a retractable cable reel having
a spring (preferably, though not necessarily a constant tension
spring) coupled to a flexible cable. The cable is attached to a
fixed support (called the "lock point") while the opposing
end of the casing is releasably attached to the tool. As the cable
is withdrawn from the casing to maneuver the tool, the spring unwinds
but exerts a retraction force on the cable to retract the cable
when the tool is placed closer to the lock point. The distal end
of the cable is provided with a clasp which is adapted to be connected
to the fixed support, such as a ladder, a bench top located at hip
level or higher, or the worker's tool belt, for example, thus providing
the lock point.
 The tension on the retractable cable is constant and such
that the worker may readily maneuver the tool. The cable extends
or shortens without overt action by the user and without having
to overcome a substantial retraction force. The weight of the safety
device is not substantial and does not add significantly to the
weight of the tool. In short, the worker is not impeded substantially
in the flexibility or utility of the tool, yet the tool users and
surroundings are protected.
 The retractable reel securing the cable includes a hub which
is provided with a plate which contains ratchet teeth on its periphery,
and the ratchet plate rotates in opposite directions as the cable
is extended or retracted.
 Inside the casing, a sliding lock plate is located beneath
the ratchet plate of the retractable cable in the normal use (or
upright) position, and has a configuration and teeth corresponding
to the teeth of the ratchet plate, which are asymmetrical (preferably
a sawtooth configuration) to prevent cable payout when the lock
plate engages the hub in the inverted position of the casing. When
the casing is in an upright position (that is, the tool clasp is
located above the lock point at which the cable clasp is attached),
the lock plate is disengaged from the ratchet plate of the retractable
reel by gravity, thereby permitting unimpeded use of the tool.
 Should the tool fall, as it is falling toward the horizontal
level of the lock point, the reel retracts the cable, shortening
the distance below which the tool may fall. As the tool falls sufficiently
past this horizontal level of the lock point, the cable, acting
as a tether, causes the casing to invert. This rotation, in turn,
causes the lock plate to fall under gravity relative to the retractable
reel. The spring continues to exert a retracting force on the cable,
and the cable continues to rewind until the tool falls to the level
at which the tool tries to extend the cable against the force of
the spring. At this point the reel attempts to rotate in a counter
direction and the weight of the tool firmly locks the reel against
any further extension of the cable. The lock plate is restrained
against rotation in the casing of the device, and this prevents
any further extension of the cable and halts the downward movement
of the tool because the distal end of the cable is latched to a
rigid support (at the lock point).
 The present invention provides a reliable, fast-acting,
economical and light-weight safety tether or device for hand tools
actuated by the fall itself, and preventing damage as well as injury.
 Other features of the present invention will be apparent
to persons skilled in the art from the following detailed description
of a preferred embodiment accompanied by the drawing wherein identical
reference numerals will be used to refer to like parts in the various
BRIEF DESCRIPTION OF THE DRAWING
 FIG. 1 is an upper isometric view of the tool safety device
of the present invention with the major components in exploded relation;
 FIG. 2 is an upper isometric view of the device of FIG.
1 from the same side as FIG. 1 but looking in an opposing direction;
 FIG. 3 is a side vertical view of the device of FIG. 1 in
assembled relation with the right (i.e., ratchet) housing member
removed and with the device in the normal upright use position,
showing the lock plate disengaged from the ratchet plate;
 FIG. 4 is a view similar to FIG. 3 with the device inverted
and showing the lock plate engaging the ratchet plate and securing
the cable reel;
 FIG. 5 is a vertical sectional view of the device of FIG.
1 along sight line 5-5 of FIG. 3.
DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENT
 Referring to FIGS. 1 and 2 reference numerals 10 and 11
respectively designate first and second housing sections which cooperate
to form a casing or outer housing. For convenience, and as will
be better understood from the following description, the first housing
section 10 is sometimes referred to as the left or spool housing;
and the second housing section 11 is sometimes referred to as the
right or ratchet housing. Housing sections 10 11 cooperate to provide
an outer housing 19 (FIG. 5) enclosing the cable reel and lock plate.
 The two housing sections 10 11 differ in some interior
structure, but their peripheries are mirror images of one another,
and they are designed with engaging edges to form a closed casing
which encloses a retractable cable reel generally designated 14
and which is mounted on a shaft 15 the ends of which are mounted
respectively to the spool housing section 10 and the ratchet housing
section 11 as further described below.
 Cable reel 14 includes a hub 12 comprising a cylindrical
wall 13 and a ratchet plate 16 forming a spool 18 which houses
a constant-tension spring 20 coiled within the spool 18 and a cover
plate 22 which serves as an end plate for the spool, whereas the
ratchet plate 16 acts as the opposing end plate for the spool. The
end plates 22 16 maintain the spring within the housing formed
by the spool 18 while permitting the spring 20 to exert a retraction
(i.e. rewind) force on the cable 28 wrapped about the hub 12 as
will be described.
 A lock plate 24 is located within the housing sections 10
11 in such a manner, as will be described, that it may freely slide
in a radial (upward in FIG. 1) direction relative to the reel when
the outer housing 19 is inverted--that is, in a plane generally
perpendicular to the axis of shaft 15 (which axis defines the "axial"
direction). Moreover, a slot 23 or receptacle in which the lock
plate 24 is slidably received and guided is formed by cooperating
structure of the housing section 11 and the ratchet plate 16 such
that the lock plate 24 is free to slide in a radial plane aligned
with the plane of (and guided by) the ratchet plate 16 as can be
seen in FIG. 5 and will be further understood from subsequent description.
 A first attachment device in the form of an openable clasp
26 is secured by means of an annular recess 25 (FIG. 1) in the base
of the clasp, to the top of the casing formed by the housing sections
10 11 when they are assembled. Clasp 26 provides an attachment
device for reasonably securing the safety device to the tool sought
to be protected against damage, which is not shown for brevity.
Other tool attachment devices are readily available; or the retractable
reel mechanism could be housed in the tool itself, thereby obviating
the need for the tool clasp 26 and independent casing sections 10
 Flexible cable (including wire, coated wire strand or cloth
cord) 28 forms a tether and is wound about the outer surface cylindrical
wall 13 of the hub 12. An inner or proximal end 27 of the cable
28 is secured to the hub 18 and thus to the outer or distal end
of the spring 20 as is known in the art of retractable cable reels.
Thus, the spring biases the cable to be wound about the hub 12 thereby
tending to retract the cable into the housing, while permitting
the cable to be extended with little effort as long as the hub is
free to rotate. The inner end of the spring 20 is fixed to a splice
17 in the shaft 15 which shaft is constrained against rotation.
The right end of the shaft 15 is formed into a hex head 17A which
is received in a corresponding hex recess 17B formed in right housing
section 11. A cable clasp or clamp generally designated 30 is secured
to the distal end 29 of cable 28.
 Before describing the structure in greater detail, a better
understanding of the device and its operation may be obtained, it
is believed, by a general description.
 When the first and second housing sections 10 11 are assembled
together and secured by the shaft 15 (FIG. 5), they form a casing
or outer housing for the retractable cable reel 14 which is free
to rotate on the shaft 15. The inner end of the spring 20 is secured
to the fixed shaft 15 which is secured against rotation to the
housing sections 10 11 by the hex head 17A in recess 17B. Alternatively,
the shaft 15 could be formed integrally with one or both sidewalls
of the housing, as persons familiar with the art with appreciate.
 The cable 28 is wrapped around the cylindrical surface 13
of the spool 18 and has its proximal end 27 fixed to the distal
end of the spring 20 as described. The spring 20 is a constant
tension spring--that is, it exerts a substantially constant retraction
force (clockwise in FIG. 1) on the cable 28 substantially independent
of the length of the cable 28 which is retracted or payed out from
the casing. The remainder of the cable is wound about the outer
surface of the cylindrical wall 13 of spool 18 as mentioned, and
the cable 28 extends through the bottom of the casing as viewed
in FIG. 1 preferably through a brass eyelet.
 In use, the clasp 26 (and thus the outer housing 19) is
secured to a tool desired to be protected as described; and the
cable clasp 30 is attached to a support. The support may be a rigid
structure such as a hook on a ladder or on a bench, or it may be
attached to the tool belt or other suitable location on the person
performing the work and using the tool.
 In this example, it is assumed that the tool is being used
at an elevation above the attachment point of the cable clasp 30
this point sometimes being referred to as the lock point.
 In the normal use position, the outer housing 19 is upright
in that the lock plate 24 is disengaged from the cable reel 14 (see
FIG. 6). The cable 28 may be readily extended as the tool and housing
11 are elevated, and similarly, the cable is be retracted within
the spool as the tool (and tether device) are lowered, permitting
the worker to maneuver the tool as needed, and shortening the length
of the extended portion of the cable.
 If the tool should be dropped or otherwise fall from its
location above the lock point, the initial movement of the tool
and casing would be comparatively slow and the cable will retract
automatically onto the spool and become shortened as the elevation
of the tool approaches the elevation of the lock point (that is,
as the vertical distance between the tool and the lock point becomes
shorter). As the tool drops below the elevation of the lock point,
the casing inverts so that the lock plate 24 is now above the ratchet
plate 16 but the two are still aligned, compare FIGS. 6 and 7.
Thus, as the device inverts, the lock plate 24 falls a short distance
radially inward (downward) relative to the position of the axis
of the shaft 15 in the inverted position (FIG. 7). The lock plate
24 engages and locks the ratchet plate 16 preventing further rotation
of the cable reel 14 in the "unwind" or "pay out"
direction, thus securing the tool to the lock point at a shorter
vertical displacement than the starting length of the unwound portion
of the cable--i.e. typically substantially less than the original
distance at which the tool was being used above the lock point,
and avoiding a damaging impact to the tool or surroundings, that
otherwise might have occurred.
 Still referring to FIGS. 1 and 2 it will be observed that
FIG. 1 is an upper perspective view, with the major components in
exploded relation, looking into the interior of the ratchet housing
section 11 whereas FIG. 2 is a similar view, but looking into the
interior of the spool housing section 10. Turning then to the drawing,
the spool or hub 12 includes the cylindrical side wall 13 which
is rigidly affixed to the ratchet plate 16 and houses the spring
20. The outer end of spring 20 is turned over at 20A and fits into
a recessed slit 20B in the cylindrical wall 13 to anchor the spring.
The side wall 13 includes a number of tabs 35 which originally extend
in an axial direction, and are received in corresponding slots 36
formed in the spool cover 22 and then bent inwardly to secure the
spool cover 22 to the hub 12 and, in cooperation with the solid
ratchet plate 16 to form an enclosure for the coiled spring 20.
 The spring 20 is a flat metal spring of the type known as
"constant tension", and has a proximal or inner end is
bent inwardly at 39 (FIG. 5) and received in a retaining slot 40
formed in the shaft 15. As described, the shaft 15 is fixed relative
to the housing sections 10 11 thus the proximal or inner end 39
of the spring 20 is also fixed or attached to the casing.
 The peripheries of the ratchet plate 16 and the spool cover
22 extend radially beyond the circumferential side wall 13 of the
spool 18 thus cooperating with cover 22 to form a circumferential
recess 31 (FIG. 5) for receiving the flexible cable 28 as it is
wrapped around the outer surface of the cylindrical wall 13 between
the ends of the spool thus formed.
 The outer (right) surface of the ratchet plate 16 (FIG.
5) is formed into a series of teeth 42 each tooth being asymmetrical,
generally in the form of a sawtooth, and formed to fit into mating
sawtooth recesses in a correspondingly formed upper edge 44 of the
lock plate 24 so that when the two are engaged, the spool cannot
rotate in an unwind direction (clockwise in FIG. 4) relative to
the lock plate 24 which, as will be understood, is fixed against
rotation within the casing, although it may slide radially.
 Turning now to the ratchet housing section 11 as seen in
FIGS. 1 2 and 5 it includes an end wall 46 and a side wall 47
extending about the perimeter and defining an edge 48. The inner
center of end wall 46 is formed into a boss 49 which forms recess
17B having a hexagram interior shape and which receives the hex
end of shaft 15 to prevent rotation of the shaft 15. A screw 50
is threaded into a tapped hole extending axially into the hex head
17A of the shaft 15 to secure the shaft to the right housing section
11. The spool housing section 11 may be molded of synthetic material
such as plastic, or it may be metal for greater durability and strength.
 Cable reel 12 is rotatably mounted on the shaft 15 (FIG.
5). A pair of opposing walls 52 53 (FIG. 1) are formed in the interior
of the ratchet housing section 11 and integral with the end wall
46 and peripheral side wall 47 for rigidity. The opposing walls
52 53 are spaced to form receptacle 23 for the lock plate 24 permitting
the lock plate to slide easily, but preventing the lock plate from
rotating about an axis parallel to the shaft 15.
 Laterally, the lock plate 24 is retained on its inner side
by the peripheral edge 54 of the ratchet plate 16 (FIG. 5). On the
outboard side of the lock plate 24 a pair of elongated bumpers
55 55 are formed (FIGS. 2 5) each provided with a rounded surface
55A (FIG. 5) to reduce friction. The spacing between the inner surface
of the housing end wall 48 and the opposing circumferential surface
of the outer edge 54 of the ratchet plate 16 is less than the combined
width of the lock plate 24 and bumpers 55 so that when the device
is inverted, the teeth 44 of the lock plate 24 are aligned with,
and will engage the teeth 42 of the ratchet plate, as may be observed
by comparing the free position of the lock plate 24 in FIG. 3 (in
which the unit is upright) with the locked position of lock plate
24 in FIG. 4 (with the unit inverted). As seen in FIG. 2 the teeth
44 of the lock plate 24 are also in the form of a sawtooth and conform
to, and mate with, the teeth 42 of the ratchet plate 16.
 The left end of the shaft 15 (which is split as will be
recalled) is pressed into an aligned opening 51 in a boss formed
on the inner surface of the left side casing 10. It will be observed
that the shaft 15 serves not only to mount the retractable cable
reel assembly 14 for rotation, but the shaft 15 also provides a
rigid connection for securing the two housing sections 10 11 together
forming a rigid casing for mounting and securing the interior components.
 An eyelet 89 (FIG. 2) is placed in the bottom of the side
wall 47 of the outer housing through which the cable 28 extends.
The cable is also placed through a bumper 90 and around a thimble
91 which is coupled to the previously described swivel clamp or
hook 30. The cable is fixed to the thimble 91 by swage 92.
 Turning now to FIGS. 3 and 4 the release and locking positions
of the sliding lock plate 24 are illustrated. It will be appreciated
that FIGS. 3 and 4 are views looking into respectively the spool
housing 10 (the ratchet housing 11 being removed), and that the
portion of the casing for mounting the locking plate 24 which confines
and guides the lock plate 24 (sometimes referred to as a receptacle)
is not seen here because it is located in the ratchet housing section
11--i.e. walls 52 and 53 (see FIG. 1).
 Turning then to FIG. 3 the spool housing 10 is seen in
a first upright or normal use position. The tool is attached to
the upper clasp 26 fixed to the top of the casing, and the clasp
30 which is connected to the distal end of cable 28 wound on the
constant tension retractable cable reel 14 is attached to a fixed
lock point preferably located beneath the range of normal operating
height for the tool being protected. When the tool is being maneuvered,
the cable 28 unwinds (i.e. extends from the position of FIG. 3)
or retracts as needed; and the reel 16 is free to rotate, exerting
a constant retraction force on the cable 28.
 If the tool were to fall, initially reel 14 would normally
tend to retract the cable 28 (i.e. reel 14 would rotate counter
clockwise in the direction of the arrow 60 in FIG. 3). When the
tool and safety device pass the horizontal plane of the lock point,
the clasps invert, and so does the safety tether device, as illustrated
diagrammatically by the large arrow A between FIGS. 3 and 4. In
the inverted position, as illustrated in FIG. 4 it will be appreciated
that the rewind direction for the reel is still clockwise, as the
arrow 60 in FIG. 4 indicates. Thus, if there is slack in cable 28
the reel will retract the cable because in the rewind direction
of rotation, the teeth of the reel 14 will override the teeth of
the lock plate 24. However, when the weight of the tool tends to
extend the cable 28 as the tool falls, the teeth of the lock plate
interfere with, and lock the teeth of the reel, thus preventing
further pay out of the cable. In practice, the weight of the tool
provides sufficient force so that when the cable is retracted and
the falling tool exerts a force on the cable tending to extend it,
the rotation of the hub 12 is reversed quickly, and due to the asymmetrical
shape of the tether on the lock plate 24 and ratchet plate 16 the
two snap firmly and quickly into locking position to end the fall
of the tool immediately. The lock plate 24 guided by the receptacle
23 in which it is slidably received, falls under gravity and engages
the ratchet plate 16. The teeth 42 44 engage and stop the rotation
of the cable reel instantly. This arrests the fall of the tool and
prevents impact with the floor or ground.
 By clipping the clasp 26 (i.e. the one directly attached
to the casing) to the worker (as at his or her belt), the inventive
device can be used as a "parking" or personal retention.
Moreover, by incorporating the reel, lock plate and cable into the
tool casing, the clasp 26 and housing sections 10 and 11 may be
 Having thus disclosed one embodiment, persons skilled in
the art will be able to modify certain of the structure which has
been disclosed and substitute equivalent elements for those illustrated
while continuing to practice the principle of the invention. For
example, the durability and strength of the device may be increased,
thus a corresponding cost increase, for different applications.
For example, the housing sections 10 11 may be made of metal. Alternatively,
the tool clasp 26 may be attached to a bracket mounted on the interior
of the outer housing and supporting the cable reel 14 on a shaft
carried by the bracket. The bracket, in turn, would serve as a mounting
for the outer housing sections 10 11. By using a metal bracket
of this type, durability and strength can be improved. Moreover,
as noted above, the outer housing sections 10 11 could be the housing
or casing for the tool itself, and this would eliminate the need
for the tool clasp 26. It is thus intended that all such modifications
and substitutions be covered as they are embraced within the spirit
and scope of the appended claims.