Self-locking brake for portable stand

A brake for a portable stand includes a bracket for attaching the brake to the stand, a sleeve attached to one edge of the bracket, and a plunger movable within the sleeve. A toggle joint, connected between the bracket and one end of the plunger, has a pivot plate as one arm of the toggle joint and a handle attached to the pivot plate for extending and retracting the plunger. A foot attached to the free end of the plunger is either a friction pad or a caster and is attached to the plunger by a leveling screw. The edge of the bracket includes a recess for receiving the toggle joint in an over-center position.

BACKGROUND OF THE INVENTION 
This invention relates to a brake for a portable stand and, in particular, 
to a brake which is rugged and self-locking yet can be easily set and 
released. 
Stands, carts, and the like have long been provided with wheels to enable 
them to be moved without being lifted. Brakes have been provided, 
typically adjacent at least two wheels, for holding a stand in place. 
There are many types of brakes, all of which lower a foot to the floor and 
slightly lift the stand or at least bear a substantial fraction of the 
weight of the stand. Of the many types of brakes, this invention relates 
to brakes which use a combination of toggle joint and plunger, such as 
described in U.S. Pat. No. 2,712,366--Skupas--and in U.S. Pat. No. 
3,735,841--Auriemma. In the Skupas patent, a pair of bell crank levers and 
links straddle a telescoping leg and are attached to each end of the leg. 
In the Auriemma patent, a compound lever extends a square tube held on 
three sides by a bracket attached to a cart. 
For tool stands in particular, commercially available brakes are not strong 
enough to bear the weight of the tool, permitting the stand to rock or 
move when the tool is used. In a brake such as disclosed in the Auriemma 
patent, the tube is not held sufficiently securely to prevent motion when 
a force is applied at a large (relative to the height of the brake) 
distance from the floor. Heavy tools such as jointers and table saws make 
the problem more severe because their center of gravity is high. 
Another problem is setting and releasing the brake. Brakes typically 
include an over-center mechanism in which the weight of the stand, and 
whatever is on the stand, bears down on the brake, locking the brake in an 
extended position. A toggle joint is typically designed for ease in 
setting the brake but not for ease in releasing the brake. While this 
assures that the brake is securely set, the brake is often difficult and 
inconvenient to release. The Auriemma patent discloses using an auxiliary 
lever for releasing the brake to solve this problem. While effective, the 
brake mechanism described in the Auriemma patent is complicated and 
expensive. The brake described in the Skupas patent relies on separate 
foot pedals for setting and releasing the brake and the pedals are 
inconveniently located close to the underside of the cart. 
For tool stands which are frequently moved, by contractors for example, the 
brake mechanism must be rugged and easily operated. It is highly desirable 
that the brakes on one side of a stand be ganged and actuated 
simultaneously by a common bar or handle. In addition, the brakes should 
be actuated wherever a force is applied along the handle, i.e. it should 
not be necessary to apply a force at the center of the handle to actuate 
the brakes simultaneously. 
The number of power tools and tool stands sold each year is considerable. 
Typically the tool stands do not include wheels or brakes. Presently 
available aftermarket kits are not rugged enough to withstand use or to 
hold the tool in place without rocking. There is thus a need for a brake 
kit for adding wheels and brakes to tool stands. 
In view of the foregoing, it is therefore an object of the invention to 
provide a brake suitable for use on stands for heavy tools. 
Another object of the invention is to provide a self-locking brake that is 
easily set and released. 
A further object of the invention is to provide a brake that does not 
permit wobble or other motion of the brake when the brake is set. 
Another object of the invention is to provide a brake kit which can be 
attached easily to existing portable stands. 
A further object of the invention is to provide a brake which can be ganged 
with like brakes and actuated simultaneously. 
SUMMARY OF THE INVENTION 
The foregoing objects are achieved in the invention in which a brake for a 
portable stand includes a bracket for attaching the brake to the stand, a 
sleeve attached to one edge of the bracket, and a plunger movable within 
the sleeve. A toggle joint connected between the bracket and one end of 
the plunger has a pivot plate as one arm of the toggle joint and a handle 
attached to the pivot plate for extending and retracting the plunger. A 
foot attached to the free end of the plunger is either a friction pad or a 
caster and is attached to the plunger by a leveling screw. The edge of the 
bracket includes a recess for receiving the toggle joint in an over-center 
position. A kit for tool stands includes bracing for the legs of the tool 
stand and at least two brakes interconnected by a handle.

DETAILED DESCRIPTION OF THE INVENTION 
FIG. 1 illustrates the legs of a portable stand such as would be used for 
supporting a table saw. Legs 11-14 are each a strip of sheet metal bent at 
ninety degrees along its length and angled to form a taper. Tools stands 
as sold by various hardware stores typically include just four legs and a 
horizonal platform for holding a tool. In order to move the tool, the tool 
and stand must be lifted and relocated. 
In accordance with the invention, wheel set 18, described in more detail in 
conjunction with FIG. 7, is included in a kit with brakes to enable the 
tool stand to be moved about without having to lift the stand. A pair of 
brakes 20 and 21 are attached to adjoining legs one side of stand 10 for 
holding the stand in place. Brake 20 includes handle 23 for setting and 
releasing brake 20 and brake 21 includes handle 24 for setting and 
releasing brake 21. Handles 23 and 24 are interconnected by bar 25 for 
simultaneous actuation of brakes 20 and 21. Although not shown in FIG. 1, 
a second set of brakes can be attached to legs 11 and 14. 
The construction of brakes 20 and 21 is shown in greater detail in FIGS. 2 
and 3. FIG. 2 illustrates brake 20 in a set or extended position and FIG. 
3 illustrates brake 20 in a retracted or released position. Brake 20 
includes bracket 31 for attaching the brake to leg 12, e.g. by way of 
bolts 32 and 33. Bracket 31 is preferably angle iron having one flange 
connected to leg 12 and the other flange extending away from leg 12 and 
terminating in edge 34. 
Sleeve 35 has its longitudinal axis parallel to edge 34 and sleeve 35 is 
attached along its length to edge 34, for example by welding. Plunger 36 
is a rod extending from both ends of sleeve 35 and can move up and down 
within the sleeve. At lower end 37, foot 39 is attached to plunger 36 by 
leveling screw 41 which is threaded into the lower end of plunger 36. Foot 
39 preferably includes friction pad 43 for engaging a floor or other 
support surface. The upper end of plunger 36 is attached to link 45 by 
bolt 46, about which link 45 can pivot. The free end of link 45 is 
attached to one corner of pivot plate 47 by bolt 48. Pivot plate 47 is a 
rectangular plate attached at a second corner to bracket 31 by bolt 49. 
Bolts 48 and 48 are at adjacent corners of rectangular pivot plate 47. 
A toggle joint is a device having two links or arms jointed together end to 
end but not in line such that a force applied to the joint tending to 
straighten out the device will force the free ends of the links apart. It 
can be shown that when the links are in a nearly straight line, there is a 
considerable mechanical advantage; i.e. the force applied to the joint is 
considerably less than the force provided at the free ends of the joint. 
In FIGS. 2 and 3, link 45 is one arm of a toggle joint and the side of 
pivot plate 47 between bolts 48 and 49 forms the other arm of the toggle 
joint. In brake 20, the toggle joint also includes an over-center 
mechanism by which the brake is held in an extended or set position by the 
weight of the stand. The over-center mechanism can be seen by comparing 
FIGS. 2 and 3. When brake 20 is set, bolt 48 is to the left of a line 
connecting the centers of bolts 46 and 49. When brake 20 is retracted, 
bolt 48 is to the right of the line connecting the centers of bolts 46 and 
49. When brake 20 is set, bolt 48 rests in recess 51 in edge 34. Since 
plunger 36 is supporting part of the weight of the stand, the upward force 
on plunger 36 forces link 45 counter-clockwise against recess 51, locking 
the brake in the set position. 
Handle 23 is attached to pivot plate 47 by bolts 53 and 54. Preferably, 
handle 23 is parallel with the side opposite the first side which formed 
one arm of the toggle joint. When brake 20 is set, handle 35 extends 
vertically downward from the toggle joint and provides a compact brake 
unit. 
As illustrated in FIG. 3, brake 20 is readily released by rotating handle 
23 counter-clockwise, forcing bolt 48 over center and raising plunger 36. 
Brake 20 is held in a released position by frictional engagement of 
plunger 36 with sleeve 35. The length of handle 23 is considerably greater 
than the distance between bolts 48 and 49, giving the user a further 
mechanical advantage in setting or releasing the brake. 
FIG. 4 illustrates an alternative embodiment of the invention in which a 
caster is attached to the lower end of plunger 36. While a single pivot 
plate and link could be used to connect bracket 31 to the upper end of 
plunger 36, it is preferred to use a pair of pivot plates straddling edge 
34 and handle 23, as shown in FIG. 4. Pivot plates 47a and 47b are located 
on each side of handle 23 and edge 31 (not shown). Similarly, link 45a and 
link 45b straddled pivot plates 47a and 47b and are connected to the upper 
end of plunger 36, which is preferably flattened to provide clearance for 
links 45a and 45b. 
Instead of a separate brake and caster, caster 61 is attached to the lower 
end of plunger 36. In this embodiment of the invention, the stand is 
portable when plunger 36 is extended, lowering caster 61 below the end of 
leg 12, and the stand is fixed when plunger 36 is retracted. 
As illustrated in FIG. 1, brake 20 is attached to a leg of a stand and the 
legs are tapered or splayed. To assure that plunger 36 is vertical, edge 
34 is not parallel to the flanged attached to a leg but has a 
complementary taper to maintain plunger 36 vertical. 
FIGS. 5 and 6 illustrate an alterative embodiment of the invention in which 
bracket 31 is adapted to be fastened to a horizontal support. Bracket 71 
includes an elongated vertical flange having edge 72, to which sleeve 73 
is attached. Edge 72 includes recess 75, which corresponds to recess 51 in 
FIG. 3, and recess 76, which provides clearance for bolt 81 when brake 70 
is retracted. Bracket 71 includes a second flange 82 attached to a 
horizontal support by bolt 85 and 86. The operation of brake 70 is the 
same as the operation of brake 20. 
FIG. 7 illustrates a portion of the wheel set used in a kit including 
brakes constructed in accordance with the invention. Since a portable 
stand is likely to be moved a great deal, four braces are included in the 
kit for stiffening the legs. The intersection of two leg braces is shown 
in FIG. 7 in which brace 91 is attached to brace 92 and caster 93 by four 
bolts. The braces are attached to both sides of a leg by bolts through 
holes such as hole 96. Each leg brace is a predetermined length of sheet 
metal bent to form two sides having an included angle corresponding to the 
taper, if any, of legs. The taper or splay is represented in FIG. 7 by 
dot-dash lines 97 and 98. When braced, the legs of the portable stand are 
considerably stiffer, preventing bending or twisting of the legs as the 
stand is moved about. Two casters and two straight wheels are included in 
the kit, one wheel for each corner formed by the braces. The casters are 
attached at adjoining corners. Four casters could be used, but this might 
make the stand difficult for one person to steer. 
The wheel set and brakes provide a secure, sturdy, portable stand having 
brakes that are easily set and released. Plunger 36 fits closely within 
sleeve 35, preventing wobble. 
Having thus described the invention, it will be apparent to those of skill 
in the art that various modifications can be made within the scope of the 
invention. For example, although described in a preferred embodiment as a 
brake for a portable tool stand, a brake constructed in accordance with 
the invention can be used for other applications such as appliances or 
light trailers. The bracket need not be a separate element but can be part 
of a stand having a built-in brake. The shape of the handle and bar can be 
modified to suit the application or aesthetics.