WO2000065668A1

WO2000065668A1 - Improved hammer for a piezoelectric actuator and method for producing same

Info

Publication number: WO2000065668A1
Application number: PCT/CN1999/000061
Authority: WO
Inventors: Tak Chi Sher
Original assignee: Polycity Enterprise Limited
Priority date: 1999-04-26
Filing date: 1999-04-26
Publication date: 2000-11-02
Also published as: CN1328703A; JP2002543365A; DE19983943T1; CN1178306C; DE19983943B4

Abstract

An enhanced hammer for a piezoelectric actuator having integral arms extending horizontally from a ring body supported by a hammer body member. The hammer body member has a vertically extending elongated axle for centering the ring member. The ring member rests upon the base portion of the body member. The ring and base are molded as separate unitary pieces which are then fitted together to form the complete hammer assembly.

Description

IMPROVED HAMMER FOR A PIEZOELECTRIC ACTUATOR AND METHOD FOR PRODUCING SAME

BACKGROUND OF THE INVENTION

The present invention relates to a unique hammer used in piezoelectric actuators.

Specifically the present invention provides a hammer body with integral outwardly extending

hammer arms and a method for producing the same.

Existing hammers as used in piezoelectric actuators are composed of two separate

component parts— a hammer body and a hammer pin. To date there has not been a hammer

in one unit, i.e., the hammer body and pin molded together, by die cast molding, nor has

there been a hammer with a hole through the hammer body by die cast motding. The

technical problems of molding such a small piece have not been overcome.

Presently, assembly of the hammer pin into the hammer body necessitates drilling a

hole through the hammer body. The drilling of such a small hole through the hammer body

which is also miniature in size is very difficult. For best performance of the hammer, the

hammer pin must be fixed at the center point of the hammer body and in an absolutely

balanced, horizontal and symmetric manner. This is very difficult to achieve for technical

reasons during assembly of the hammer pin into the hammer body.

In the present invention, the hammer still consists of 2 parts. Yet, it is not necessary

to drill a hole through the hammer body. Furthermore, the center point of the hammer body

and the balance, horizontaJity and symmetricalness of the hammer arms is guaranteed in the

-1-

SUBSTTTUTE SHEET (RULE 2B) process of the present invention. The performance of the finished product using this newly

invented hammer is therefore enhanced.

SUMMARY OF THE INVENTION

The present invention is a two-part hammer for a piezoelectric actuator wherein the

horizontal hammer arms are integrally molded into the hammer ring member. A hammer

body member having a vertically extending axle supports and retains the ring member by

extending through a central opening in the ring.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 illustrates a cross-sectional view of a prior art hammer within a piezoelectric

actuator.

Fig. 2A illustrates an exploded perspective view of a first prior art hammer.

_fig. 2B shows a side elevation view of the first prior art hammer of Fig. 2A.

Fig. 2C illustrates an exploded perspective view of a second prior art hammer.

Fig. 2D shows a side elevation view of the second prior art hammer of Fig. 2C.

Fig. 3A illustrates an exploded perspective view of the hammer of the present

invention.

Fig. 3B shows a side elevation view of the hammer of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Fig. 1 illustrates in a cross-sectional view of a prior art hammer 11A within a

piezoelectric actuator. The operation of such devices is well known in the art. The actuator

operates by the collision of the hammer 11 A with other parts of the actuator to generate an

-2-

SUBSTTΠΠΈ SHEET (RULE 26) electric charge. Any deviation in the balanced, symmetrical construction of the hammer 1 1A

will affect the stability of the emission of the electric charge from the actuator.

Figs. 2A-2D also illustrate prior art hammers. Fig. 2A is an exploded view of the

two-part hammer 1 1. It has a hammer body member 12 and a hammer pin 14. A hole 16

must be drilled through the body 12 to accept the pin 14. The drilling is done after the body

has been molded. Pin end 18 is pressed into the hole 16 and must be exactly in the center

of the body 12 to be absolutely balanced and horizontal with the extended arms 22 and 24

perfectly symmetrical.

Another prior art hammer 1 1 A is shown in Figs. 2C and 2D. Again, pin 14A must

be pressed into drilled hole 16A with the arms 22A and 24 perfectly symmetrical, balanced,

and horizontal within the body 12 A.

-The present invention is shown in Figs. 3A and 3B. Hammer 11 C has a guaranteed

center point with perfect balance, horizontal arms, and symmetric arms because the arms 22C

and 24C are formed by unitary molding. The arms are formed in the molding process and

are, therefore, integral to the ring body 30. The hammer arms are not formed by a pin

passing through a delicately drilled hole as is known in the prior art. Hammer ring body 30,

made of metallic or non-metallic materials, such as plastic, is a generally cylindrical tube

with a vertically extending, central opening 34 with perpendicularly extending arms 22C and

24C. By forming the arms in the mold improved symmetry and balance of the hammer is

achieved.

The hammer 1 1 C is assembled by placing ring 30 over hammer body member 40,

which is made of metal. Hammer body member 40 has a cylindrical base portion 42 with

^■ -

SUBSTTTUTE SHEET (RULE 26) a shoulder 44. Extending upwardly from the center of the base portion 42 is an elongated

cylindrical axle member 46. When assembled, the underside 36 of the ring 30 is pressed

against the shoulder 44 of the body member 40.

The outer surface 48 of the elongated axle 46 may be fixed or fitted tightly against

the inner surface 38 of the ring 30 by various means. Depending upon the composition of

the ring 30, there may be a certain degree of elasticity of ring 30, the diameter of the inner

hole 34, thus, may be slightly less than the diameter of the elongated axle 46 (the axle having

a diameter the same as or slightly greater than the hole). Alternatively, the inner surface 38

may be provided with protruding vertical strips 50 which when the ring 30 is wholly

squeezed onto the elongated axle 46 will fit tightly against the inner surface 38 and the strips

50 to hold the ring 30 on the body member 40. Thus, an improved hammer is^~produced.

_ Although the invention has been described with reference to a specific embodiment,

this description is not meant to be construed in a limiting sense. On the contrary, various

modifications of the disclosed embodiments will become apparent to those skilled in the art

upon reference to the description of the invention. It is therefore contemplated that the

appended claims will cover such modifications, alternatives, and equivalents that fall w thin

the true spirit and scope of the invention.

Claims

CLAIMS:

1. A hammer for a piezoelectric actuator comprising:

a hammer ring member having two perpendicularly extending integral arms and a

central opening; and

a hammer body having a base portion and an upwardly extending axle member, said

axle member extending through said central opening of said hammer ring,

said hammer ring member seated on said base portion of said hammer body.

2. The hammer of claim 1 wherein said axle member is generally cylindrical having a

diameter slightly less than said central opening to ensure a tight fit between said axle

member and said central opening.

3. The hammer of claim 1 wherein said central opening has protruding vertical strips for

urging against an outer surface of said axle member to ensure a tight fit between said axle

member and said central opening.

4. The hammer of claim 3 wherein said axle member is generally cylindrical.

5. The hammer of claim 1 wherein said ring member is made of molded plastic and said

hammer body is made of metal.

-5-

SUBSTTTUTE SHEET (RULE 26

6. The hammer of claim 5 wherein a diameter of said central opening of said hammer

ring is same as or slightly less than a diameter of said axle member.

7. A method for producing a hammer for a piezoelectric actuator comprising the steps of:

molding a unitary hammer ring member having two perpendicularly extending

integral arms and a central vertical opening;

molding a hammer body having a base portion and an upwardly extending axle

member;

pressing said unitary ring onto said hammer body with said axle member extending

through said central opening and said ring seated on said base portion.

8. The method of claim 6 wherein said hammer ring member is made of plastic material

and said hammer body is made of metal materials.

-6-

SUBSTTTUTE SHEET (RULE 26)