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Description  |
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BACKGROUND OF THE INVENTION:
This invention relates generally to the class of hand tools known commonly
as lawn and/or leaf rakes. More specifically, the present invention is
concerned with an improved molded plastic lawn rake head which includes a
frame section composed of a first, synthetic resin and a tine section
composed of a second, selected synthetic resin having physical properties
differing from those of the first synthetic resin.
Molded plastic leaf or lawn rake tool heads of various designs and
constructions have been available for purchase on the open market for many
years. Typical of these molded plastic leaf rakes is one illustrated and
described in U.S. Pat. No. 3,724,188 issued Apr. 3, 1973 to Eads (U.S. Cl.
56-400.17; Int. Cl. A1d 7/00) which proposes that the rake head be molded
or formed in its entirety of polypropylene or like synthetic resin and
which summarizes certain advantages of a molded plastic leaf rake head
over the older steel or bamboo rake heads.
It has been found, however, that molded plastic leaf rake heads formed
from, or composed of, a single thermoplastic resin, such as polypropylene,
or polyethylene, while being comparatively inexpensive to manufacture, are
lacking in certain physical characteristics or qualities, such as
strength, durability, resiliency and eye appeal, which are desired by the
average purchaser and user of lawn rakes. Furthermore, due to the
comparative weakness of polypropylene and its low modulus of elasticity,
the tines of a rake head formed therefrom must be relatively wide and
thick to attain sufficient stiffness to enable them to function with any
degree of efficiency.
SUMMARY AND OBJECTS OF THE INVENTION
The present invention provides an improved molded plastic lawn rake head
which comprises an integral, generally fan-shaped frame section composed
of a first, comparatively inexpensive, low modulus synthetic resin having
a narrower end portion formed with a handle-receiving socket, an opposite,
wider end portion formed with a multiplicity of longitudinally disposed,
relatively spaced apart, outwardly opening sprue channels connected by a
common, transversely disposed manifold chamber, a longitudinally tapered,
thin-walled intermediate portion extending between and the end portions of
said frame section and having a series of longitudinally extending
stiffing ribs projecting outwardly from opposite faces thereof; and an
integrally molded tine section composed of a second, comparatively
tougher, more elastic, wear-resistant synthetic resin and having a root
portion molded in and occupying the sprue channels and manifold chamber,
and a multiplicity of elongated, resilently flexible tines integrally
connected with the root portion and extending longitudinally outwardly
from the wider end portion of the frame section.
In a preferred embodiment of this invention, the manifold chamber formed in
the wider end portion of the frame section includes a plurality of lateral
passages opening on opposite faces of the frame section and the root
portion of the tine section includes a plurality of integral, lateral
projections extending through the lateral passages of the manifold chamber
to interlock the tine section with the frame section of the rake head.
A principal object of this invention is to provide a molded plastic lawn
rake head which possesses the resilently flexibility and durability of a
steel lawn rake head, but which is comparatively lighter and less
expensive to manufacture and has considerably more eye appeal than the
conventional steel lawn rake head.
Another object of the invention is to provide a molded plastic leaf rake
head which includes a multiplicity of tines which are so formed and
arranged as to render the rake head substantially self-cleaning in its
normal operating mode.
A further object is to provide a molded plastic lawn rake head which may be
fabricated in a conventional, two stage, insert injection molding process
in which a fan-shaped frame section is first formed from a relatively
inexpensive, low modulus synthetic resin having a selected coloration, and
in which a tine section is subsequently formed of a second, stronger,
stiffer and more durable synthetic resin having a color contrasting with
that of the frame section. The two stage molding procedure provides
integral joining of the tine section with the frame section without any
clearance whatsoever.
These and other objects and advantages attendant to the present invention
will become more readily apparent from the following description and the
appended drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a top plan view of a plural resin, molded plastic lawn rake head
according to the present invention;
FIG. 2 is a side elevation view of the lawn rake head;
FIG. 3 is a forward end elevational view of the rake head;
FIG. 4 is a bottom plan view;
FIG. 5 is an end elevational view looking toward the handle-receiving
socket of the rake head;
FIG. 6 is an enlarged, fragmentary sectional view taken approximately along
the line 6--6 of FIG. 1;
FIG. 7 is an enlarged, fragmentary cross-sectional view taken along the
line 7--7 of FIG. 1;
FIG. 8 is an enlarged, fragmentary, sectional view taken approximately
along the line 8--8 of FIG. 2;
FIG. 9 is an enlarged, detailed sectional view taken along the line 9--9 of
FIG. 2; and
FIG. 10 is a similar view taken along the line 10-10 of FIG. 2.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENT
With reference to the drawings, it will be seen that the present lawn rake
comprises an integral, molded frame section 15 which is preferably
composed of a readily available, inexpensive thermoplastic synthetic resin
having a comparatively low modulus of elasticity, such as polypropylene,
or polyethylene. The frame section 15 includes a relatively narrower end
portion 16, an opposite, relatively wider end portion 17 and a
longitudinally tapered, comparatively thin-walled intermediate portion 18
which extends between and integrally connects the opposite end portions 16
and 17 of the frame section 15. The narrower, butt end portion 16 is
formed with a handle-connecting means preferably in the form of a tapered
or screw-threaded socket 19. As will be understood, the socket 19 is
arranged to receive a cooperatively tapered, or screw-threaded end portion
of an elongated handle, not shown. The narrower end 16 of the frame is
also preferably formed with a boss and coved hole socket 20 through which
a locking screw or nail may be passed radially into the handle-receiving
socket 19 to lock an associated handle member therein.
The intermediate, fan-shaped portion 18 of the frame is formed with a
comparatively thin, planar base wall or panel 21 bounded along its
marginal edges with perpendicular related edge flanges 22 and formed in
its central area with a series of relatively spaced apart, longitudinally
extending stiffening ribs 23. The ribs 23 project outwardly from the
opposite faces of the base panel 21 and merge with a transverse rib or
flange 24 formed at the juncture of the intermediate portion with the
relatively wider outer end portion 17 of the frame. On the under face
(FIG. 4) of the rake head, the marginal flanges 22 and stiffening ribs 23
merge with corresponding flanges 25 and reinforcing ribs 26 formed on the
narrower, socket end section 16. On its upper face (FIG. 1) the flanges 22
and reinforcing ribs 23 merg with a flat plate-like panel 27 which may
advantageously be used to display indicia, not shown, identifing the
country of origin, model number, etc. of the rake head.
In addition to the fan-shaped frame section 15, the rake head also
comprises an integrally molded tine section indicated generally by
reference numeral 28. The tine section 28 of the rake head is composed of
a second, thermoplastic, synthetic resin, such as ABS (terpolymer,
acrylonitrile-butadiene-styrene), or a polycarbonate resin (Lexan), having
substantially greater strength and wear-resistance than the synthetic
resin from which the frame section 15 is formed. Preferably, the resin
from which the tine section 28 is formed is colored or pigmented to
provide a color contrasting with that of the frame section 15, thus
providing an attractive, decorative appearance for the rake head and
adding substantially to its eye appeal.
As will be readily understood by those skilled in the art of injection
molding, the present rake head may be formed by utilizing a conventional,
two-stage, insert molding procedure in which the frame section 15 of the
rake head is first formed in a molding chamber of desired configuration
and thereafter the tine section 28 is injection molded in an adjacent
molding cavity which is in communication with the wider, outer end portion
of the previously molded frame section 15.
Toward this end, the wider end portion 17 of the frame 15 is formed to
include a multiplicity of longitudinally disposed, relatively spaced
apart, outwardly opening sprue channels 29 and a transversely extending,
common manifold chamber 30 which intersects the sprue channels 29
intermediate their ends (see FIGS. 6-8). The common manifold chamber 30
extends transversely for substantially the entire width of the wider end
portion 17 of the frame 15 and is in direct communication with an open,
coextensive slot 31 formed in the under face of the frame (see FIGS. 4 and
6). The manifold chamber 30 also communicates with a plurality of
relatively spaced apart gate openings 32 formed in the opposite, upper
face of the frame.
The tine section 28 is formed to include an anchoring, root portion 33 and
a multiplicity of elongated, resilently flexible tines 34 radiating
outwardly from the outer end portion 17 of the frame. The root portion 33
of the tine section includes a transversely extending rib or flange 35
which adjoins the roots of the tines 34 along the wider, outer end portion
17 of the frame section 15. The root portion 33 further includes a
continuous, transverse runner 36 which fills the transverse manifold
chamber 30 and which connects a plurality of relatively spaced apart,
longitudinally extending runners 37 which occupy the sprue channels 29.
As will be seen in FIG. 6 of the drawings, the root portion 33 of the tine
section 28 also includes a plurality of integrally formed lateral
projections 38 and 39 which extend laterally outwardly through the slot 31
and gates 32, respectively, of the frame section and which function to
interlock the root portion 33 of the tine section 28 within the upper end
portion 17 of the frame section 15. Also, if desired, the lateral
projections or formations 39 may include relatively enlarged head portions
40 in the shape of alphabetical letters or other indicia which may form a
trademark for the rake head. The relatively enlarged head portions 40 of
the lateral projections 39 are easily molded into desired letter-forming
indicia by inserting an appropriately shaped mold plate or insert into the
molding cavity during the second stage injection molding of the tine
section 28 of the rake head.
The tines 34 are preferably formed on their upper surfaces with integral,
longitudinally coextensive stiffening ribs 42, and relatively widened root
portions 43 adjacent the transverse base web 35. Also, the root portions
43 of the tines 34 may be additionally strengthened and reinforced by
tapered ribs 44 formed on their under surfaces (see FIG. 9).
Each of the tines 34 terminates in an angularly bent tip or finger portion
45 whose length dimension ranges from one-fourth to one-third of the
overall length of the tine. This unusually long length of working finger
greatly increases the longevity and useful life of the rake head, since it
is the fingers or tips of the tines which are subjected to continuous
frictional wear during normal usage of the lawn rake.
Further, the unusually large length dimension of the tips or finger
portions 45 of the tines is believed to contribute to what has been
observed as a self-cleaning action on the part of the tines. In this
regard, it has been observed that as the tines 34 of the rake head are
moved across the ground surface in normal raking action they tend to
vibrate in non-cyclic fashion with the result that the out of phase
vibration of the tines tends to remove leafs which have become impaled on
the fingers 45 of the tines. Further, the ABS resin from which the tines
are formed has a comparatively low coefficient of friction and a high
degree of lubricity which also aids in the separation of impaled leafs
from the outer finger portions of the tines.
The use of polypropylene or other comparative low modulus, inexpensive
synthetic resin in the formation of the frame section of the rake head
substantially reduces the overall cost of the rake head as contrasted to
one formed entirely from a more costly, high strength resin, such as the
ABS or polycarbonate resins. At the same time, the use of the more
expensive, high strength resins in the formation of the tine section of
the rake head greatly improves the mechanical action of the tines and the
longevity of the overall rake head.
By utilizing different synthetic resins for the frame and tine sections of
the rake head, each section may be formed throughout with a color
contrasting with that of the other section, thus providing a highly
decorative and novel, eyepleasing appearance for the overall rake head.
For example, the visable portions of the tine section, namely: the tines
themselves, the exterior adjoining rib 35 and the indicia providing
projections 40 may be formed with a grey coloration, while the frame
section may be pigmented throughout to provide a contrasting green, black,
or red color. The contrasting colors of the frame and tine section greatly
increases the sales appeal of the rake head as compared with that of a
unicolored molded plastic rake head.
While a single perferred embodiment of this invention has been illustrated
and described in detail, it should be understood that various
modifications as to details of construction and design may be resorted to
without departing from the spirit of the invention or the scope of the
following claims.
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