Hand-held gardening machine

A hand-held gardening machine includes a pair of upper and lower clipper blades each formed with clipper teeth. The clipper blades are caused to slidably reciprocate in a longitudinal direction thereof by means of output from a power source. A comb-like safety plate is formed with protrusions protruding beyond the tips of the teeth. The positions at which the protrusions of the safety plate are located are selectable from overlapping positions of the teeth of the clipper blades and positions shifted from the overlapping positions.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a hand-held gardening machine such as a 
hedge trimmer. In particular, a hand-held gardening machine comprising a 
pair of upper and lower clipper blades which are caused to reciprocate. 
2. Description of the Prior Art 
In general, a hand-held gardening machine of this type uses output from a 
power source such as an internal combustion engine or an electric motor to 
cause a pair of upper and lower elongate clipper blades to reciprocate 
relative to each other in a longitudinal direction thereof. 
In recent years, various safety standards as safety measures have been 
tending to be established in many countries in view of increasing 
accidents caused in working such as trimming operation. For example, a 
trimmer comprising clipper blades falls under such safety standards, 
because an operator is exposed to a possible danger, in particular, a 
serious accident due to contact between the clipper blade(s) and 
operator's leg or the like during operation. To meet such requirements, a 
comb-like safety plate is mounted above or below the upper and lower 
blades supported slidably each other. FIG. 8 shows a clipper blade working 
portion of such a hand-held gardening machine. 
In FIG. 8, clipper blades 40, 50 which are laid one on top of the other are 
held, for example, between a comb-like safety plate 60 having protrusions 
61, 61, . . . which is located below the bottom surface of the lower 
clipper blade 50 and a supporting plate 70 which is located above the top 
surface of the upper clipper blade 40, and supported slidably to-and-fro 
by means of mounting means 71 such as a screw. 
The protrusions 61, 61, . . . are so formed that tips thereof protrude 
beyond tips of the teeth 41, 41, . . . and 51, 51, . . . by d.sub.1 (for 
example, 8 mm or more). It is prescribed in the safety standard (UL 
standard) that when operator's leg M of a diameter assumed to be, for 
example, 120 mm is brought in contact with the protrusions 61, 61 of the 
safety plate 60 which are adjacent to each other, the distance between the 
tip of the tooth 41 or 51 and the portion of the leg M which is closest 
thereto is d.sub.2 (for example, 4 mm or more), in terms of safety 
measures. 
As seen from FIG. 8, each of the pitches between neighboring teeth 41 and 
41 and between neighboring teeth 51 and 51 of the upper and lower clipper 
blades 40, 50 and the pitch between neighboring protrusions 61 and 61 of 
the safety plate 60 are formed to be equal. 
As shown in FIG. 8 by the solid line, the teeth 41, 41, . . . and 51, 51, . 
. . are so mounted as to overlap each other at their starting points of 
stroke (hereinafter referred to as a first dead center). In the following 
description, explanation will be given only on neighboring two teeth 41, 
51, and protrusions 61, 61 as a matter of convenience. Needless to say, 
however, the same operation is true of other counterparts. 
The upper and lower blades 40, 50 are respectively formed with elongate 
holes 42, 52 which allow relative movement thereof with respect to the 
screw 71 (the supporting plate 70) so that the teeth 41, 51 initiate 
reciprocating motion from the first dead center as a starting point and 
overlap again at the position shown in FIG. 8 by the chain-double dotted 
line (hereinafter referred to as a second dead center) to terminate 
forward stroke. The longitudinal length of each of the elongate holes 42, 
52 is equal to stroke S (travel) of each of the teeth 41, 51, and this is 
equal to the distance between the first dead center and the second dead 
center. 
The protrusion 61 of the safety plate 60 is so fixedly mounted by means of 
the screw 71 as to overlap the overlapping position of the teeth 41, 51 at 
their first dead centers. 
By this structure, the upper tooth 41 at position II and the lower tooth 51 
at position I when present at their first dead centers are adapted to 
overlap together at position III when present at their second dead centers 
and then return to the original positions at the end of return stroke. In 
this connection, the relationship between the positions I, II, III and the 
stroke S is as shown in FIG. 3. Thus, the upper and lower teeth 41, 51 is 
adapted to cut a plant A or the like in the course of the forward stroke 
from the first dead center to the second dead center. 
In such a conventional hand-held gardening machine as described above, 
however, a plant or the like having a small diameter is likely to be 
caught in the gap between the tooth 41 or 51 and the protrusion 61 during 
the return stroke of the tooth 41 or 51 from the second dead center to the 
first dead center. Inconveniently, as described later in detail, it is 
difficult to cut the thus caught plant completely because no edge is 
formed on either side of the protrusion 61 of the safety plate 60. In such 
a condition that the slender branch or the like is involved as a foreign 
obstacle in the gap between the tooth 41 or 51 and the protrusion 61, 
there is a problem that the upper and lower clipper blades 40, 50 are 
prevented from smoothly reciprocating to result not only in lowered 
operational efficiency but also in increased power loss. 
SUMMARY OF THE INVENTION 
The present invention has been made in view of the problems inherent in the 
conventional hand-held gardening machine. It is, in particular, an object 
of the present invention is to provide a hand-held gardening machine which 
is capable of attaining optimum application of the safety plate according 
to objects to be trimmed or operational situation, thereby enabling 
ensured safety and improved operational efficiency to be realized, and yet 
which is capable of attaining improved durability of a hand-held gardening 
machine to be attained. 
To attain the above-mentioned objects, a hand-held gardening machine 
according to the present invention comprises: 
a pair of upper and lower clipper blades each formed with clipper teeth, 
said clipper blades being caused to slidably reciprocate in a longitudinal 
direction thereof by means of output from a power source; and 
a comb-like safety plate formed with protrusions and mounted above or below 
the teeth, tips of said protrusions protruding beyond the tips of said 
teeth; 
and characterized in that positions at which said protrusions of said 
safety plate are located are selectable from overlapping positions of said 
teeth of said clipper blades and positions shifted from said overlapping 
positions. 
In the hand-held gardening machine according to the present invention which 
is constructed as described above, positions at which said protrusions of 
said safety plate are located are selectable from overlapping positions of 
said teeth of said clipper blades and positions shifted from said 
overlapping positions. By virtue of this, the positions where the teeth of 
the clipper blades perform their strokes relative to the protrusions of 
the safety plate can be shifted by shifting the mounting position of the 
safety plate.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Now, an embodiment of the present invention will be described with 
reference to the accompanying drawings. FIG. 1 is a plan view showing an 
embodiment of a hedge trimmer as one of the hand-held gardening machines 
according to the present invention. FIG. 2 is a perspective exploded view 
of a clipper blade working portion. In the drawings given for illustrating 
embodiments of the present invention, the same reference number are 
allotted to the parts as allotted to the corresponding parts of the 
above-described conventional hand-held gardening machine shown in FIG. 8 
to eliminate overlapping explanation. 
The illustrated trimmer 10 comprises a driving portion 12 and a working 
portion 20 detachable from the driving portion 12. The driving portion 12 
includes an outer case 13 having its rear end horizontally mounted with a 
rear handle 14, and an electric motor (not shown) fixedly disposed in the 
outer case 13. 
On the other hand, the working portion 20 includes a pair of upper and 
lower clipper blades 40 and 50, and a casing member 22 covering the rear 
ends of the clipper blades and composed of vertically separable parts. The 
upper and lower blades 40 and 50 each has a plurality of substantially 
triangular teeth 41, 41 and 51, 51 . . . , respectively. Onto the upper 
portion of the casing member 22, a base 24b of a front handle 24 having a 
grip portion 24a is fixed by means of screws 28, 28, and a hand guard 29 
is fixed in front of the front handle 24 by means of screws. 
Although no particular illustration is given, rotational driving force of 
the motor in the driving portion 12 is transmitted to the upper and lower 
clipper blades 40, 50 via a conventional means such as an eccentric cam, 
thereby causing the upper and lower clipper blades 40, 50 to reciprocate, 
in opposite phases with each other, in the longitudinal direction thereof. 
As shown in FIG. 2, the structure of the working portion of the clipper 
blade according to the present invention are basically the same as that of 
conventional one, and hence detailed explanation is omitted. In addition 
to the conventional structure, however, the structure of the present 
invention has the following additional characteristic structural feature. 
In the safety plate 60 are formed by perforation two mounting holes 62a, 
62b which enable adjustment of the relative position between the safety 
plate 60 and the upper and lower clipper blades 40, 50. The distance 
between the mounting holes 62a and 62b is set to be, for example, in the 
illustrated embodiment, half of stroke S (travel) of reciprocating motion 
of each of the upper and lower teeth 41, 51. In other words, as described 
in detail below, the traveling positions of the teeth 41, 41, . . . and 
51, 51, . . . relative to the protrusions 61, 61, . . . are shifted 
between a condition where the screw 71 is inserted through the inner 
mounting hole 62a for mounting the safety plate 60 and another condition 
where the screw 71 is inserted through the outer mounting hole 62b for 
mounting the safety plate 60. Accordingly, the overlapping position of the 
upper and lower teeth 41, 51 is shiftable by half of the stroke, i.e., S/2 
relative to the protrusion 61. 
FIGS. 3 and 4 show one mode of use of the working portion in the clipper 
blade of the embodiment according to the present invention shown in FIG. 
2. In this illustrated mode, the screw 71 is inserted through the inner 
one 62a of the mounting holes of the safety plate 60 and screwed into a 
nut 72. 
The embodiment employing the mode shown in FIGS. 3 and 4 exhibits the same 
function as that of the conventional one shown in FIG. 8, and hence 
detailed description is omitted. Incidentally, FIG. 4 shows the upper and 
lower teeth 41, 51 in the course of the return stroke from the second dead 
center to the first dead center. In FIG. 4, the upper and lower teeth 41, 
51 are shown in mid course of returning from the overlapping position 
(second dead center) at the position III to the dead centers at the 
positions II and I, respectively. If a plant or the like A' of a small 
diameter is caught in a gap L between the upper tooth 41 and the 
protrusion 61 at the position II in the course of the return stroke, it is 
difficult to cut the plant or the like A' completely because no edge is 
formed on either side of the protrusion 61. In such a condition that the 
plant A' is involved in the gap L as a foreign obstacle, the upper and 
lower clipper blades 40, 50 are prevented from smoothly reciprocating to 
result not only in lowered operational efficiency but also in increased 
power loss, as described above. 
As is understood from the above description, although the embodiment 
employing the mode illustrated in FIGS. 3 and 4 is not suitably used for a 
plant and the like A' having a relatively small diameter, it is capable of 
cutting a plant A having a diameter substantially equal to the distance 
between the protrusions 61, 61 neighboring .each other (maximum cuttable 
branch diameter). 
On the other hand, FIGS. 5 and 6 show the other mode of use of the working 
portion in the clipper blade of the embodiment according to the present 
invention shown in FIG. 2. In this illustrated mode, the screw 71 is 
inserted through the outer mounting hole 62b of the safety plate 60 and 
screwed into a nut 72. The positional relationships between the upper and 
lower teeth 41, 51 in FIGS. 5 and 6 corresponds to the above-described 
positional relationships therebetween in FIGS. 3 and 4, respectively. In 
other words, FIG. 5 shows the teeth in forward stroke from the first dead 
center (shown by a solid line) to the second dead center (shown by a 
chain-double dotted line). On the other hand, FIG. 6 shows teeth in the 
course of return stroke from the second dead center to the first dead 
center. 
The embodiment employing the mode of use illustrated in FIGS. 5, 6 is 
basically the same as the above-described embodiment employing the mode of 
use illustrated in FIGS. 3, 4 and is different therefrom only in that the 
safety plate 60 and, in consequence, the protrusions 61, 61 are located at 
the position shifted in one direction (left direction in FIGS. 5, 6) by 
half of the stroke S/2 relative to the teeth 41, 51 of the upper and lower 
clipper blades 40, 50. Accordingly, overlapping explanation is omitted. 
Also in the mode shown in FIGS. 5, 6, as in the mode shown in FIGS. 3, 4, 
the upper tooth 41 and the lower tooth 51 are adapted to be present at the 
position II and the position I, respectively, when they are at their first 
dead centers, and to overlap each other at the position III when they are 
at their second dead centers. 
Thus, as in the mode in FIG. 3, a plant or the like B is cut in the course 
of forward stroke from the first dead center to the second dead center 
(see FIG. 5). 
On the other hand, also in the course of return stroke from the second dead 
center to the first dead center, a plant or the like B' is unfailingly cut 
off (see FIG. 6). Further, as is apparent from FIG. 6, a branch or the 
like is prevented from being caught between the tooth 41 or 51 and the 
protrusion 61, thereby enabling occurrence of incomplete cutting to be 
eliminated. 
Accordingly, in this illustrated mode, although the maximum cuttable branch 
diameter is small as compared with the condition shown in FIGS. 3 and 4, 
even a plant B' having relatively small diameter or the like is 
unfailingly cut off. 
As described above, in this embodiment, the relative positional 
relationship between the overlapping position of the teeth 41, 51 formed 
on the upper and lower clipper blades 40, 50 and the protrusion 61 formed 
on the safety plate 60 is adjustable in the longitudinal direction by 
changing the mounting hole 62a or 62b through which the screw 71 is 
inserted, thereby enabling suitable manner for use to be attained 
according to objects to be trimmed and type of operation. Accordingly, 
improved operational efficiency can be realized. 
In the next place, another embodiment of the working portion of the clipper 
blades according to the present invention will be described with reference 
to FIG. 7. In FIG. 7, the same reference numbers are allotted to the parts 
as allotted to the functionally equivalent parts of the embodiment shown 
in FIGS. 2 to 6. Accordingly, overlapping explanation is omitted. 
In the embodiment illustrated in FIG. 7, as the upper and lower clipper 
blades 40 and 50, there are used double-toothed clipper blades 
respectively formed with teeth 41a, 41a, . . . , 41b, 41b, . . . , and 
51a, 51a, . . . , 51b, 51b which extend, in pairs along the longitudinal 
axes thereof, in right and left directions relative to the longitudinal 
direction thereof. In this connection, the pitch between the teeth and the 
stroke S of the upper and lower clipper blades 40, 50 are the same as 
those of the embodiment shown in FIGS. 2 to 6. A solid line and a 
chain-double dotted line show overlapping positions of the teeth at the 
first and second dead centers, respectively. 
With respect to the embodiment shown in FIG. 7, in the side on which the 
upper and lower teeth 41a, 51a, i.e., ones of the above-mentioned pairs 
are provided (upper side in FIG. 7), the protrusion 61a of the safety 
plate 60 is so located as to overlap with the overlapping position of the 
teeth 41a and 51a at the first dead center, as in the mode shown in FIGS. 
3 and 4. 
On the other hand, in the side on which the upper and lower teeth 41b, 51b, 
i.e., the others of the pairs are provided (lower side in FIG. 7), the 
protrusion 61b of the safety plate 60 is so located as to be shifted by 
half stroke (S/2) from the overlapping position of the teeth 41b and 51b 
at the first dead center, as in the mode shown in FIGS. 5 and 6. 
In this embodiment, there are provided in combination the structure 
corresponding to the mode shown in FIGS. 2 to 4 in one side along the 
longitudinal direction of the upper and lower clipper blades 40, 50 (upper 
side in FIG. 7) and the structure corresponding to the mode shown in FIGS. 
5 and 6 in the other side (lower side in FIG. 7). Accordingly, in this 
embodiment, the right side of the clipper blades 40, 50 on which the teeth 
41a, 51a are formed and the left side on which the teeth 41b, 51b are 
formed can selectively be used without changing the mounting hole 62a or 
62b through which the screw 71 is inserted. Consequently, suitable manner 
for use can readily be attained according to objects to be trimmed or type 
of operation. 
In the above, the specific embodiments of the present invention have been 
described in detail. However, it should be understood that the present 
invention is by no means restricted to the embodiments, and that various 
modifications may be made without departing from the scope of the 
invention defined by the claims. 
For example, the distance between the mounting holes 62a and 62b for the 
screw 71 is not restricted to half stroke S/2 but may be appropriately 
selected. Further, the mounting holes are not restricted to being formed 
at two positions and may of course be formed at more positions. 
Incidentally, it is also possible that screws 71 are placed at the same 
intervals at positions appropriately shifted from the dead centers of the 
clipper blades 40, 50 and mounting holes 62 one-to-one corresponding to 
the screws 71 are formed in the safety plate 60 and the safety plate 60 is 
mounted in reversed manner in the longitudinal direction. 
As understood from the above description, according to the present 
invention, optimum application of the safety plate can be attained which 
is well-adapted to objects to be trimmed or operational situation, thereby 
enabling ensured safety and improved operational efficiency to be 
realized, and yet improved durability of a hand-held gardening machine can 
be attained.