Key touch adjuster for a keyboard musical instrument

For easy and free adjustment of key touch on a keyboard musical instrument, a balancer made of an elongated leaf spring has a pair of opposed leg sections suited for elastically clamping hammer shank or hammer wood of the action assembly. Preferably, the balancer is provided with pawls for stable attachment by encroachment on the objective.

BACKGROUND OF THE INVENTION 
The present invention relates to a key touch adjuster for a keyboard 
musical instrument, and more particularly relates to an improvement in 
construction of an action assembly of a keyboard musical instrument such 
as a piano. 
On a keyboard musical instrument such as a piano, an action assembly is 
driven for operation by depression of an associated key to strike an 
associated string, and vibration of the string is amplified by a sound 
board to generate an intended sound. 
Key touch, i.e. reaction of a key on the player's fingers, is set to a 
standard magnitude in general by embedding a weight such as a lead piece 
in the key at a preselected position. Since performance is greatly swayed 
by key touch on the player's fingers, key touch of a key should preferably 
match player's personal preference. However, personal preference differs 
greatly from player to player. For example, in the case of training at 
music schools, relatively heavy key touch is preferred for training of 
students' fingers. Such heavy key touch is, however, in general unsuited 
for personal preference of skilled or players. In order to adjust key 
touch of a key, one need to use a weight somewhat heavier than the 
standard. In other words, replacement of weight is necessary for adjusting 
key touch in accordance with player's personal preference. Such 
replacement is a troublesome work which requires time and labour. In 
addition, after removing an old weight, the old hollow for the old weight 
has to be closed by a wooden piece. For these reasons, it has been quite 
infeasible to freely and easily adjust key touch on a keyboard musical 
instrument all that long. 
SUMMARY OF THE INVENTION 
It is the object of the present invention to enable free and easy key touch 
adjustment on a keyboard musical instrument in accordance with players' 
personal preference. 
According to the basic aspect of the present invention, at least one 
balancer is detachably coupled to the hammer of an action assembly of a 
keyboard musical instrument.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 shows one typical example of the action assembly for a grand piano 
to which the present invention is well applicable. The action assembly 
includes a wippen 6 pivoted at the rear end to a wippen rail 7 via a 
wippen flange 8 and supported about the middle by a capstan (not shown) 
secured to the rear end of an associated key. The other end of the wippen 
6 pivotally supports a jack 9. A repetition lever flange 10 secured to the 
wippen 5 pivotally supports a repetition lever 11 above the wippen 5. 
Above the repetition lever 11 is pivoted a hammer 12 to a hammer shank 
flange 13 on a shank flange rail 14. Near the pivot the hammer 12 is 
provided with a hammer roller 15 which rests on the top face of the 
repetition lever 11. The repetition lever 11 is accompanied with a 
repetition spring 16 whose repulsion pushes up the repetition lever 11 in 
order to register the hammer 12 at the initial rest position. The hammer 
12 includes a hammer shank 12a, a hammer wood 12b and a hammer felt 12c. 
The jack 9 extends upwards through the repetition lever 11 and its top 
abuts against the hammer roller 15. 
On key depression, the wippen 6 swings upwards to toss the hammer 12 via 
the jack 9. After striking an associated string (not shown), the hammer 12 
moves to resume its initial rest position due to repulsion of the spring. 
Shock caused by this returning motion of the hammer 12 is borne by the 
repetition lever 11 and a hammer shank felt (not shown) mounted to the 
wippen. As briefly stated above, one or more balancer is detachably 
coupled to the hammer of the action assembly in accordance with the 
present invention. 
One embodiment of the key touch adjuster is shown in FIG. 2 in which the 
key touch adjuster 20 includes a balancer 30 attached to the hammer shank 
12a of the hammer 12. The balancer 30 takes the form of a leaf spring 
extending in the longitudinal direction of the hammer shank 12a and having 
a pair of opposed leg sections 30a, 30b and a connecting section 30c. The 
two leg sections 30a and 30b are biased towards each other so that, when 
the balancer 30 is attached to the hammer shank 12a, they should 
elastically clamp the hammer shank 12a in order to keep the attachment. 
Another embodiment of the key touch adjuster is shown in FIG. 3, in which 
the key touch adjuster 20 includes a balancer 40 attached to the hammer 
shank 12a of the hammer 12. The balancer 40 takes the form of a leaf 
spring extending in the longitudinal direction of the hammer shank 12a and 
having a pair of leg sections 40a, 40b and a connecting section 40c. The 
leg sections 40a and 40b are both semicircular in transverse cross 
sectional profile and the largest distance between the two leg sections 
40a and 40b in a free state is smaller than the smallest transversal size 
of the hammer shank 12a so that, when the balancer 40 is attached to the 
hammer shank 12a, they should elastically clamp the hammer shank 12a in 
order to keep the attachment. 
The other embodiment of the key touch adjuster is shown in FIG. 4, in which 
the key touch adjuster 20 includes a balancer 50 attached to the hammer 
shank of the hammer 12. The balancer 50 takes the form of a leaf spring 
extending in the longitudinal direction of the hammer shank 12a and having 
a longitudinal slit. The slitted ends of the leaf spring is fastenable by 
a connector 51. The largest traversal size of the leaf spring in a 
fastened state should be smaller than the smallest transversal size of the 
hammer shank 12a so that, when the balancer 50 is attached to the hammer 
shank 12a, it should elastically clamp the hammer shank 12a in order to 
keep the attachment. 
When the key touch adjuster 20 such as shown in FIGS. 2, 3 or 4 is attached 
to the hammer shank 12a of the hammer 12, the weight of the hammer shank 
12a is increased accordingly and a greater force is required to toss the 
hammer roller 15 by the jack 9. This in turn results in heavier key touch 
on the player's fingers. 
In addition, since the key touch adjuster 20 is elastically attached to the 
hammer shank 12a and made of a simple leaf spring, the key touch adjuster 
20 can be replaced and its position on the hammer shank 12a can be 
changed, both quite easily and instantly in order to freely and easily 
adjust key touch in accordance with player's personal preference. Further, 
when compared with conventional weight change on a key, a small change in 
weight of the key touch adjuster and/or in its position can bring about 
effective increase in moment. Standard key touch is easily resumed simply 
by detaching the key touch adjuster 20 from the hammer shank 12a. 
Instead of the hammer shank 12a, the key touch adjuster 20 may be attached 
to the hammer wood 12b of the hammer 12. 
With the above-described constructions, there may be a case in which the 
elastic attachment allows unexpected displacement of the key touch 
adjuster from the initial set position due to vibrations of related parts 
during performance. The embodiment of the key touch adjuster shown in 
FIGS. 5A and 5B has a function to avoid such unexpected displacement. 
More specifically, the key touch adjuster 20 includes a balancer 60 given 
in the form of an elongated leaf spring. The leaf spring has a pair of 
opposed leg sections 60a, 60b and an intermediate connecting section 60c. 
In a free state, the distance between free ends of the leg sections 60a 
and 60b should be smaller than the smallest transversal size of the hammer 
shank 12a so that when attached to the hammer shank 12a, the leg sections 
60a and 60b should elastically clamp the hammer shank 12a. At both 
longitudinal ends, the connecting section 60c is provided with V-shaped 
pawls 61 projecting into the space defined by the pair of leg sections 60a 
and 60b which receives the hammer shank 12a. 
When the key touch adjuster 20 is pressed against the hammer shank 12a, the 
latter is received in the space between the leg sections 60a and 60b and 
the pawls 61 on the connecting section 60c encroach on the hammer shank 
12a in order to prohibit axial rotation and longitudinal displacement of 
the latter. 
As a substitute for the pawls 61 at the longitudinal ends of the connecting 
section 60c, a pair of pawls 62 may be formed about the enter of the 
connecting section 60a by stamping as shown in FIG. 6. Further, additional 
pawls 63 may be formed on the leg sections 60a and 60b as shown in FIG. 7. 
In general the hammer shank 12a is made of wood and its grain runs in the 
longitudinal direction. The pawls 61 and 62 (see FIGS. 5A, 5B and 6) 
extend normal to the running direction of the grain whereas the pawls 63 
(see FIG. 7) extend parallel to the same direction. The latter arrangement 
of pawls assures better encroachment on and less breakage of the hammer 
shank. The size of the pawls should be chosen so that the pawl 
encroachment should well endure vibration of related parts during 
performance. 
A further embodiment of the key touch adjuster is shown in FIG. 8, in which 
the key touch adjuster 20 includes a balancer 70 given in the form of an 
elongated leaf spring. The leaf spring has a pair of opposed leg sections 
70a, 70b and a connecting section 70c. Like the foregoing embodiments, in 
a free state, the distance between free ends of the leg sections 70a and 
70b should be smaller than the smallest transversal size of the hammer 
shank 12a so that, when attached to the hammer shank 12a, the leg sections 
70a and 70b should elastically clamp the hammer shank 12a. As a substitute 
for the pawls 61 to 63, aligned small holes 71 are formed through the leg 
sections 70a and 70b near their free ends. When the key touch adjuster 20 
is attached to the hammer shank 12a, edges of the holes 71 encroach upon 
the hammer shank 12a to prohibit axial rotation and longitudinal 
displacement of the latter. 
A modification is shown in FIG. 9, in which the balancer 70 includes 
corrugations 71 formed on the leg sections 70a and 70b and a corrugation 
72 formed on the connecting section 70c. Preferably, the direction of the 
corrugations 71 is normal to that of the corrugation 72. 
A further embodiment of the key touch adjuster is shown in FIG. 10, in 
which the key touch adjuster 20 includes a balancer 80 made of a leaf 
spring. Like the embodiment shown in FIG. 3, the leaf spring includes a 
pair of opposed leg sections 80a, 80b of a semicircular transverse cross 
sectional profile and a connecting section 80c. Saw teethes 81 are formed 
on the free ends of the leg sections 80a and 80b facing to each other. 
In a broader application of the present invention, the key touch adjuster 
can be used as a weight balancer for sport utensils such as tennis and 
badminton rackets. In particular the embodiments shown in FIGS. 5A to 9 
are suited for such an application since they well catch objectives via 
encroachment even when the objectives are moved furiously. For example, by 
attaching to a racket frame and changing its position of attachment, the 
weight balancer can easily change the center of gravity of the racket.