BACKGROUND OF THE INVENTION
The present invention relates to an improved injection molding apparatus
including power units therefor, and more particularly an injection molding apparatus
having reduced noise emissions and reduced vibration transmission, plus an improved
method for reducing noise emission and vibration transmission in an injection molding
U.S. Patent 5,707,667 (EP-A-0 778 652) by Galt, Kestle and Yetter
teaches an improved sound insulated injection molding machine including at least
one hydraulic pump and an electric motor means for powering said pump. It is desirable
to provide further improvements in the reduction of noise emission and vibration
Injection molding machines that use hydraulics as a primary source
of power transfer are all faced with the problem of noise and vibration generated
by the hydraulic system. The problem manifests itself in three ways: fluid borne
noise; structural or mechanical borne noise; and air borne noise. All three of
these may be addressed in various ways, which include both mechanical and hydraulic
modifications. However, reduction in noise emission and vibration transmission
represents a long sought after goal.
The hydraulic power source in an injection molding system is one
or more hydraulic pumps driven by an electric motor. The pumps are structurally
connected to the electric motor, as with an adapter flange, with the rotational
drive being provided by a rotary coupling. The electric motor and hydraulic pump
assembly are supported on vibration dampening pads, which are in turn fastened
to the injection molding machine base.
A characteristic of hydraulic pumps is that they have a high power
density. This means that the electrical power of the electric motor is converted
to hydraulic power in a small package. Part of this energy conversion requires
that low pressure hydraulic fluid is brought up to a high level of pressure in
a very short time. This quick rise of pressure is accomplished on many small volumes
of oil within the pump in short succession. This in turn creates high frequency
pressure pulses in both the high pressure outlet of the pump and the low pressure
inlet of the pump. The housing of the pump also vibrates due to these pulses.
The pressure pulses in the suction and pressure lines of the pump
create not only fluid borne noise but mechanical vibrations in the suction and
pressure lines. These vibrations are transmitted to the machine reservoir and
base, and also to the structure that supports the pump and motor assembly, which
is normally part of the machine base and which will be referred to herein as a
The machine reservoir, base and drip pan are usually fabricated of
the same material. For most applications this material is steel, which can be of
welded, formed or cast construction. The disadvantage of using the same material
throughout the base structure is that it will then inherently have the same natural
frequency. It is desirable to reduce vibration transmission in these structures
by designing the structures with suitable materials of different natural frequencies
since this will make the transmission of vibration energy less efficient.
The structural transmission of vibration energy may also be reduced
by adding damping elements and masses in series between the vibration energy source
and the vibration energy dissipater, i.e., the side of the reservoir which converts
some of the structural vibration energy to air borne vibration energy or sound.
The larger the masses are in this system, the less efficient the energy transfer
Hot and cold rolled steel is also highly reflective to air borne
sound energy. In efforts of noise reduction in the area of the hydraulic pumps,
the majority of the air borne noise will simply reflect off any of the structure
fabricated from steel. This would include the drip pan area under the pumps as
well as the side of the reservoir and base. It would be desirable to utilize a
suitable material that has the ability to absorb sound energy rather than one
that reflects sound energy.
Accordingly, it is a principal object of the present invention to
provide an improved injection molding apparatus which includes a power source and
which has reduced noise emission and vibration transmission characteristics, as
well as an improved method for mounting power components to an injection molding
It is a further object of the present invention to provide an improved
apparatus and method as aforesaid which is simple, convenient, inexpensive and
Further objects and advantages of the present invention will appear
SUMMARY OF THE INVENTION
In accordance with the present invention, the foregoing objects and
advantages are readily obtained.
The injection molding apparatus of the present invention comprises:
an injection molding unit; a power source for said injection molding unit including
at least one hydraulic pump and at least one motor driving said pump; the apparatus
being characterized in that it further comprises a concrete mounting base with a
mounting plate affixed thereto, said concrete mounting base and mounting plate
mounting said power source, with mounting means in the mounting plate for mounting
said power source.
The present invention also includes a method for mounting an injection
molding apparatus, which comprises: providing an injection molding unit including
a power source for said injection molding unit, said power source including at
least one hydraulic pump and at least one motor for driving said pump; the method
being characterized in that it comprises the steps of mounting said power source
on a concrete mounting base with a mounting plate affixed to said concrete mounting
base and with mounting means in the mounting plate for mounting said power source.
Further features and advantages of the present invention will appear
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will be more readily understandable from a
consideration of the accompanying exemplificative drawings, wherein:
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
- FIG. 1 shows a perspective view of the injection molding apparatus of the present
- FIG. 2 shows a top view of the concrete mounting plate of the present invention
with metal mounting plate affixed thereto;
- FIG. 3 shows a side view of the mounting plate of FIG. 3;
- FIG. 4 is a top view of the mounting plate of FIG. 2 with the power source
mounted thereon; and
- FIGS. 5-6 are perspective views of additional embodiments of the present invention.
In accordance with the present invention, an improved apparatus and
method is provided for reducing machine noise and vibration. The present invention
effectively uses a drip pan made of a material that has a different natural frequency
than steel and which has an ability to absorb sound energy while at the same time
providing effective support for the power source for the injection molding unit.
The present invention uses a drip pan made of concrete. Concrete
has a different natural frequency than steel, yet it is quite dense and is porous
enough to absorb sound energy.
In addition to the foregoing, the present invention affixes a metal
plate, preferably steel, to the concrete mounting base, with mounting means as
mounting holes, in the metal plate for mounting the power source to the concrete
base and metal plate. A reinforcing member, as a steel or other metal bar, is
also desirably affixed to the concrete base to provide additional strengthening
to the concrete base. In addition, a recessed portion is provided in the concrete
base, generally under the pumps, to provide a site to catch spilled fluids, such
as oil, and a removable plug in the concrete base covering a channel communicating
with the recess to provide a means to access the recess to drain fluid spilled
from the recess. Further, desirably a mounting strut is also provided affixed to
the concrete mounting base to provide a further site for mounting components of
the power source, as for example to mount the hydraulic pumps.
It has been found that the foregoing structure effectively reduces
noise emission and vibration transmission in an injection molding apparatus by
mounting the pump and motor assembly thereon. The features of the present invention
in a drip pan are particularly advantageous in an injection molding machine in
view of the high frequency and high level of energy vibration, the number of machine
cycles and the different types of fluids which may come into contact with the drip
FIG. 1 shows injection molding apparatus 10 of the present invention
including an injection molding unit 12 and a power source 14 for said unit 12.
FIG. 1 shows the power source spaced from the injection molding unit and FIGS.
5-6 show the power source which can be slid into an injection base recess, as
will be described below. For convenience, the injection molding unit is not shown
in FIGS. 5-6. The injection molding unit 12 is mounted on injection molding unit
base 16 and desirably includes recess 18 therein as shown in FIGS. 5-6. Power source
14 is mounted on concrete mounting base 20 in a manner to be described below which
can be slid into the injection base recess 18 as clearly shown in FIG. 6 or withdrawn
therefrom a sufficient distance to provide all around access thereto for servicing,
as with a fork lift. Obviously, electrical wiring and hydraulic hosing connections
will have sufficient length to allow the concrete base to be withdrawn a sufficient
distance to allow complete access to the power source. Thus, in the embodiments
of FIGS. 5-6, the power source 14 is substantially enclosed within the molding
unit base 16.
Thus, in the preferred embodiment of FIGS. 5-6, concrete mounting
base 20 is located under the injection unit. The power source 14 includes at least
one hydraulic pump 22, with more than one such pumps shown in the drawings, and
at least one motor 24 driving the pump or pumps, desirably an electric motor.
As clearly shown in FIGS. 1-6, concrete mounting base 20 is desirably
a rectangular structure, although any convenient shape may be employed, with a
raised platform 26 for mounting motor 24 and a recess 28 for mounting the pump
or pumps 22 and to catch any spilled fluids, such as hydraulic oil. A channel
or channels 30 is desirably formed in the concrete mounting base communicating
with recess 28 with a removable plug 32 thereon to provide a means to remove spilled
fluids from the recess. The power source 14 is connected to the injection molding
unit 12 by conventional means which will not be described in more detail.
Similarly, the injection molding unit includes conventional components, such as
clamps, molds, manifolds, platens, injection nozzles and the like, which also will
not be described in detail herein.
Base 16 of injection molding unit 12 is desirably mounted on mounting
pads 34 which may be of any convenient structure, as for example rubber coated
metal with the base affixed to the pad and the pad affixed to the floor or to a
support plate, as by screwing the base into the pad and screwing the pad into
the floor or support plate.
Similarly, motor 24 is desirably mounted on mounting pads 36 which also may be
of any convenient structure, as similar to pads 34, with the motor affixed to the
pad and the pad affixed to a metal mounting plate 38 affixed to the raised platform
26 of concrete mounting base 20 as by mounting holes 40 in the metal mounting plate.
The metal mounting plate is desirably of steel, although any convenient and suitable
material may be used, as for example, high strength plastic or other metals. The
mounting plate 38 is desirably embedded in the platform 26 of concrete mounting
At least one reinforcing member 42 is desirably embedded in the concrete
mounting base 20 to provide additional strengthening thereto, as for example one
or more metal bars or a metal mesh or grid, desirably steel.
A guide member 44 is desirably affixed to the recess 28 of concrete
mounting base 20 to support pumps 22 as by at least one strut 46 which is movable
in the guide member 44 to allow for expansion during operation.
In addition to the foregoing, the concrete mounting base 20 desirably
includes mounting pads 48 which also may be of any convenient structure, as similar
to pads 34. Alternatively, the concrete mounting base 20 may rest on mounting
provisions located on machine base 16. The mounting pads 34, 36 and 48 are desirably
located where pressure is expected to be exerted.
Naturally, there are appropriate hydraulic hose fittings and electrical
wiring connections between the power source and injection unit, but these are conventional
and will not be described in more detail herein.
Thus, in accordance with the present invention, the concrete drip
tray is desirably located under the machine base and rests on vibration reducing
pads. The motor and pumps are mounted on the drip tray and also rest on vibration
The drip tray is configured in such a manner that a recess area is
provided under the pumps surrounded by a perimeter wall of the concrete base of
sufficient height to catch a large volume of spilled oil. The draining of the
spilled oil from the recess may be conveniently accomplished by removing a plug
in the wall of the base. A plug retaining fixture may be cast into the wall of
the concrete base.
The mounting of the electric motor and pumps to the concrete mounting
base requires relatively high precision of dimension tolerances of one mount relative
to the other. This is accomplished by affixing a pre-machined plate to the concrete
base, as a steel mounting plate cast into the concrete base, which provides all
the necessary mounting holes.
The concrete mounting base or tray is designed in such a way that
it is an integral part of the power pack of the injection molding apparatus. This
design effectively reduces noise and vibration in the injection molding apparatus.
It is to be understood that the invention is not limited to the illustrations
described and shown herein, which are deemed to be merely illustrative of the best
modes of carrying out the invention, and which are susceptible of modification
of form, size, arrangement of parts and details of operation. The invention rather
is intended to encompass all such modifications which are within its and scope
as defined by the claims.