Staple fastening instrument

Disclosed is an improved hand instrument for driving staples in the form of small bits of string into sheets of soft material comprising a handgun-like body composed of a grip having a hand-operated lever fixed therein and a string ejection barrel having a hollow needle fixed at its outlet end and a slidable push rod fixed therein. The hand-operated lever is so operatively connected to the push rod that the push rod is driven and inserted in the hollow needle to eject small bits of string one after another from the hollow needle every time the hand-operated lever is pressed. The hand instrument uses a composite resilient mechanism to permit application to the hand-operated lever a fixed value of return force, thereby assuring that the hand-operated lever is used by applying a fixed value of pressing force thereto, and that one does not get much tired after using the stapler many hundred times without intermission.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to an improvement in or relating to a staple 
fastening instrument or a hand instrument for driving staples in the form 
of small bits of nylon or other resin string (Called "tag pins" or "nylon 
pins") into sheets of soft material such as selected parts of clothes or 
other goods for fixing tags or connecting together. 
2. Description of Related Art 
As shown in Japanese Patent 63-281940(A) and U.S. Pat. No. 3,924,788, such 
a hand instrument uses a single spring to cause a hand-operated lever to 
return to its original position after driving and ejecting a bit of nylon 
resin string from its hollow needle. 
The counter resilient force which is applied to the hand-operated lever so 
as to pull it toward its original position will increase linearly with the 
increase of travelling distance of the hand-operated lever in driving and 
ejecting a bit of nylon resin string from its hollow needle. The 
difference between the minimum load on the hand-operated lever at the 
initial point and the maximum load thereon at the final position of the 
travelling path of the hand-operated lever is so large that one's hand and 
arm gets badly tired after operating the hand-operated lever many hundred 
times, and in the worst situation one may suffer from tendovaginitis. 
SUMMARY OF THE INVENTION 
One object of the present invention is to provide a staple fastening 
instrument or hand instrument for driving staples in the form of small 
bits of string into sheets of soft material of selected parts of clothes 
and other goods, and for fixing tags on clothes and other goods or 
connecting together without fear of causing great tiredness in one's hand 
or arm even after using many times without intermission. 
This and other objects can be attained by designing such hand instruments 
so as to keep the load or work done by hand at a substantially fixed 
amount over the travelling distance of the hand-operated lever, and by 
reducing the maximum load to possible smallest amount. 
Specifically a hand instrument for driving staples in the form of small 
bits of string into sheets of soft material comprising a handgun-like body 
composed of a grip having an operating lever fixed therein and a string 
ejection barrel having a hollow needle fixed at its outlet end and a 
slidable push rod fixed therein, said operating lever being so operatively 
connected to said push rod that said push rod is driven and inserted in 
said hollow needle to eject small bits of string one after another from 
said hollow needle every time said operating lever is pressed, is improved 
according to the present invention in that it comprises an actuating lever 
connected to said operating lever and spring-biased to cause it to rotate 
over a predetermined angle about its pivot axle for urging said operating 
lever forward all the time, said actuating lever being connected to said 
push rod for driving it back and forth; and a composite resilient 
mechanism for urging said operating lever toward its original position, 
said composite resilient mechanism comprising a first spring means to urge 
said actuating lever toward its original position with a force increasing 
linearly with the increase of rotation angle and a second spring means to 
apply to said actuating lever a resilient force which becomes zero at the 
intermediate point of rotation, increasing in one direction on the way to 
the initial point beyond the intermediate point of rotation, and 
increasing in the other direction on the way to the final point beyond the 
intermediate point of rotation. 
The second spring means is stretched between a catch pin fixed to the 
actuating lever close to its upper end apart from its pivot axle and a 
first stationary pin fixed to the grip close to the rear side of the grip 
apart from the pivot axle of the actuating lever. 
The first spring means is stretched between the catch pin fixed to the 
actuating lever close to its upper end apart from its pivot axle and a 
second stationary pin fixed to the grip close to the lower end of the 
actuating lever. The actuating lever has an arc slot made on an imaginary 
circle drawn with its center on the pivot axle of the actuating lever, and 
the second stationary pin is loosely fitted in the arc slot of the 
actuating lever, thereby permitting the actuating lever to rotate a 
predetermined angle about its pivot axle. 
Other objects and advantages of the present invention will be understood 
from the following description of a tagging instrument according to the 
present invention, which is shown in accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring to FIGS. 1 and 2, a handgun-like body 10 has a hand-operated 
lever 12 fixed thereto to rotate about a pivot axle 11. The grip 10a of 
the handgun-like body 10 contains an actuating lever 14 and a composite 
resilient mechanism to urge the actuated lever 14 toward its original 
position. Specifically, the spring-biased actuating lever 14 when pressed, 
will yieldingly rotate a predetermined angle about its pivot axle 13, 
starting from the original or initial position (solid line) and reaching 
at the final position (broken line). The composite resilient mechanism is 
composed of a first spring 15 and a second spring 16. The first spring 15 
urges the actuating lever 14 with the counter or return force increasing 
linearly with the increase of the rotational angle of the actuating lever 
14 (see FIG. 3). On the other hand the second spring 16 urges the 
actuating lever 14 with the counter or return force which decreases 
gradually as the actuating lever 14 turns from the initial point A toward 
the intermediate point C at which the catch pin 19, the pivot axle 13 and 
the stationary pin 17 are aligned together (see FIG. 6), and once the 
actuating lever 13 begins turning beyond the intermediate point C, the 
second spring 16 urges the actuating lever 14 with the pressing or advance 
force which increases gradually with the increase of rotation of the 
actuating lever 14 (see FIG. 4). 
As seen from FIG. 1, the actuating lever 14 has a cylindrical abutment 14a 
at its lower, left corner to abut against the hand-operated lever 12, and 
it has an are slot 18 below its pivot axle 13. The are slot 18 extends on 
a part of the imaginary cycle drawn with its center on the pivot axle 13, 
and a stationary pin 17 is loosely fitted in the are slot 18 of the 
actuating lever 14. The actuating lever 14 has a catch pin 19 fixed at its 
upper end, and first and second springs 15 and 16 are fixed to the catch 
pin 19 at their one ends. In addition, the actuating lever 14 has a 
U-Shape notch 20 made at its upper end, and in the U-Shape notch 20 there 
is loosely fitted a pin 22, which is fixed to the rear end of a push rod 
21 in the barrel of the handgun-like body 10. 
By pressing the hand-operated lever 12 the actuating lever 14 is made to 
rotate about its pivot axle 13 in the direction as indicated by arrow P. 
The pivot axle 13 rises from a stationary plate 23 fixed to one inner 
surface of the grip 10a of the handgun-like body 10. 
Also, a stationary pin 24 is fixed to the stationary plate 23, and the 
first spring 15 is stretched between the stationary pin 24 and the catch 
pin 19, which is fixed to the actuating lever 14. The second spring 16 is 
stretched between the stationary pin 17 and the catch pin 19. 
A staple magazine in the barrel of the handgun-like body has a guide slot 
25 loaded with a series of small bits of nylon string. A bit of nylon 
string is selected from the bottom of the pile series to be ejected from 
the hollow needle 26 one after another every time the push rod 21 is 
driven forward. 
Now, referring to FIGS. 3 to 9, the function of the composite resilient 
mechanism is described. FIG. 3 shows how the energizing force which is 
applied by the first spring 15 to the lower end of the actuating lever 13, 
that is, the load component on the hand-operated lever 12 varies while the 
lower end of the actuating lever 13 moves from the initial point A to the 
final point B. In this particular embodiment the initial value is set to 
be 300 grams, and the energizing force increases linearly from 300 grams 
at Point A to 900 grams at Point B. 
FIGS. 4 to 7 show how the second spring 16 applies its energizing force to 
the actuating lever 14. Particularly FIG. 4 shows how the energizing force 
applied to the actuating lever 14 by the second spring 16 varies with 
angular displacement of the actuating lever 14, that is, how the load 
component on the hand-operated lever 12 varies. As shown, it is 300 grams 
at the initial point A; 0 grams at the intermediate point C at which the 
fixed pin 17, the pivot axle 13 and the catch pin 19 are aligned together; 
and -300 grams at the final point B. 
As shown in FIG. 5, when the actuating lever 14 rests on the initial point 
A (solid line in FIG. 1), the second spring 16 applies its resilient force 
to rotate the actuating lever 14 in the direction indicated by arrow X, 
thus keeping the actuating lever at the rest position. At this initial 
point A the return force which is applied to the push rod 21 to keep or 
bring it toward its original position, that is, the initial load component 
on the hand-operated lever 12 is 300 grams (maximum), gradually decreasing 
until the return force is zero at at the intermediate point C (FIG. 6) at 
which the fixed pin 17, the pivot axle 13 and the catch pin 19 are aligned 
together. 
As shown in FIG. 7, when the actuating lever 14 rotates beyond the 
intermediate point C, the energizing force of the second spring 16 is 
directed in the direction indicated by arrow Y, just opposite to the 
direction in which it is directed on the side of the initial point A. The 
energizing force with which the actuating lever 14 pushes the push rod 21 
increases to maximum (300 grams) at the final point B. This is a maximum 
value of force (-300 grams) in the negative direction as viewed from the 
point of return force to bring the actuating lever 14 to its original 
position. 
The resultant energizing force of the first and second springs 15 and 16 
applied to the actuating lever 14 varies as shown in FIG. 8. As seen from 
FIG. 8, the return force which is applied to the actuating lever 14 by the 
composite resilient mechanism, that is, the load on the hand-operated 
lever 12 remains at a substantially constant value around 600 grams from 
the initial point A to the final point B. 
Now, the tagging operation is described. The guide slot 25 is loaded with 
small bits of string, and the hand-operated lever 12 is pressed to push 
the lower end of the actuating lever 14, thereby causing the actuating 
lever 14 to rotate about the pivot axle 13. The rotating force is 
converted to the pushing force through the agency of the pin 22 loosely 
fitted in the notch 20 of the upper end of the actuating lever 14, thus 
pushing the push rod 21 forward. 
Small bits of string are driven one after another into selected parts of 
sheets of soft material of cloths or other goods, thus attaching tags to 
such cloths or other goods. While driving small bits of string, the load 
on the hand-operated lever 12 remains at a fixed value of about 600 grams. 
When releasing the hand-operated lever 12, the actuating lever 14 returns 
to the initial point A under the influence of resultant resilient force of 
600 grams, and at the same time, the hand-operated lever 12 returns to the 
original position. 
As may be understood from the above, the load on the hand-operated lever 
remains constant in operation, and the maximum load is smaller than that 
which would be if a single spring were used. For these reasons one does 
not get tired so much in hand after using the tagging instrument many 
hundred times without intermission. 
The essential feature of the present invention resides in use of the 
composite resilient mechanism, which can be advantageously applied to 
similar instruments to assure application of constant driving force in 
operation, and therefore, the present invention should not be understood 
to be limitative to the tagging instrument described above, but other 
instruments using the composite resilient mechanism according to the 
present invention fall within the scope of the present invention. Also, 
the tagging instrument described above can be modified without departing 
the spirit of the present invention.