U.S. patent number 3,880,055 [Application Number 05/421,284] was granted by the patent office on 1975-04-29 for injection pump for use in hot chamber type die cast machines.
This patent grant is currently assigned to Toshiba Kikai Kabushiki Kaisha. Invention is credited to Hiroaki Abe, Yosizo Komiyama, Zenichi Mochizuki, Hiromi Nakamura.
United States Patent |
3,880,055 |
Nakamura , et al. |
April 29, 1975 |
Injection pump for use in hot chamber type die cast machines
Abstract
In an injection pump for use in a hot chamber type die cast
machine wherein the cylinder and the stationary ring surrounding
the cylinder of the pump are made of materials having different
coefficient of thermal expansion, there are provided a plurality of
contact surfaces which permit relative movement of the cylinder and
the stationary ring. The extensions of the contact surfaces
intersect each other at or near a neutral point of thermal
expansion of the cylinder.
Inventors: |
Nakamura; Hiromi (Fuji,
JA), Mochizuki; Zenichi (Fuji, JA), Abe;
Hiroaki (Numazu, JA), Komiyama; Yosizo (Gotenba,
JA) |
Assignee: |
Toshiba Kikai Kabushiki Kaisha
(Tokyo, JA)
|
Family
ID: |
13048898 |
Appl.
No.: |
05/421,284 |
Filed: |
December 3, 1973 |
Foreign Application Priority Data
|
|
|
|
|
May 24, 1973 [JA] |
|
|
48-57202 |
|
Current U.S.
Class: |
92/170.1;
417/489 |
Current CPC
Class: |
F04B
53/162 (20130101); F01B 31/06 (20130101); F04B
15/04 (20130101); F04B 7/04 (20130101) |
Current International
Class: |
F04B
15/00 (20060101); F04B 15/04 (20060101); F01B
31/00 (20060101); F01B 31/06 (20060101); F04B
53/16 (20060101); F04B 7/04 (20060101); F04B
7/00 (20060101); F04B 53/00 (20060101); F04b
039/12 () |
Field of
Search: |
;92/169,170
;417/489,490,437 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Freeh; William L.
Attorney, Agent or Firm: Wenderoth, Lind & Ponack
Claims
What we claim is:
1. In an injection pump for use in a hot chamber type die cast
machine wherein the cylinder and the stationary ring surrounding
the cylinder of said pump are made of materials having different
coefficients of thermal expansion, the improvement which comprises
a plurality of contact surfaces which permit relative movement of
said cylinder and said stationary ring, the extensions of said
contact surfaces intersecting each other at or near a neutral point
of expansion of said cylinder.
2. The injection cylinder according to claim 1 wherein said
stationary ring is formed with two inclined surfaces near its upper
and lower ends, the extensions of said inclined surfaces
intersecting at or near the neutral point of the thermal expansion
of said cylinder, said cylinder being provided with a radial flange
having an inclined surface mating with one of the inclined surfaces
of said contact ring, said injection cylinder further comprising a
guide ring interposed between said stationary ring and said
cylinder, said guide ring being provided with an inclined surface
mating with the other of said inclined surfaces of said stationary
ring.
3. The injection pump according to claim 1 wherein said cylinder is
provided with a plurality of radial projections and said stationary
ring is provided with a plurality of dove-tail shaped grooves for
accommodating said radial projections, the extensions of the
contact surfaces between said projections and said grooves
intersecting each other at or near the axis of said cylinder.
4. The injection pump according to claim 1 which further comprises
upper and lower guide rings positioned above and below said
stationary ring to surround said cylinder, and wherein said contact
surfaces are formed between said stationary ring and said guide
rings.
5. The injection pump according to claim 2 wherein said stationary
ring is made of a material having a coefficient of thermal
expansion larger than that of the materials comprising said
cylinder and said guide rings.
Description
BACKGROUND OF THE INVENTION
This invention relates to an injection pump for injecting molten
metal into a metal mould of a hot chamber type die cast
machine.
In the hot chamber type die cast machine a metal melting furnace is
installed near the die cast machine and the molten metal from the
furnace is injected under a pressure into the metal mould of the
die cast machine by means of an injection pump with its lower
position immersed in the molten metal.
Where molten aluminum, magnesium or alloys thereof are injected,
the piston and cylinder are severely eroded by the molten metal if
they are made of an ordinary heat resistant iron base alloy. In
addition, the piston and cylinder must resist against wear caused
by friction therebetween under high temperatures. For these
reasons, it has been the practice to insert a sleeve or lining made
of heat resistant and wear resistant material such as hard ceramic
in the body of the injection pump which is usually made of cast
iron and to accommodate the piston in the sleeve. As a result, the
body of the pump has a larger coefficient of thermal expansion than
that of the sleeve and this difference in the coefficient of
thermal expansion causes a gap between the body of the pump and the
sleeve, whereby the sleeve is caused to displace in the lateral
direction. Consequently, the axes of the piston and the sleeve
become eccentric, thus causing fracture and severe wear of the
piston and the sleeve. For this reason, the hot chamber type die
cast machine has not been used widely for aluminum, magnesium and
alloys thereof.
SUMMARY OF THE INVENTION
It is an object of this invention to provide an improved injection
pump for use in a hot chamber type die cast machine capable of
maintaining the cylinder and the stationary ring or sleeve
surrounding the cylinder in exact concentric relation even when
they expand thermally.
Another object of this invention is to provide an improved
injection pump of the type referred to above capable of preventing
molten metal from reaching the contact surfaces between the
cylinder and the stationary ring.
Still another object of this invention is to provide an improved
injection pump capable of simplifying the construction and reducing
the cost of manufacturing the pump.
According to this invention these and further objects can be
accomplished by providing an injection pump for use in a hot
chamber type die cast machine wherein the cylinder of the pump and
the stationary ring surrounding the cylinder are made of materials
having different coefficient of thermal expansion, characterized in
that there are provided a plurality of contact surfaces which
permit relative movement of the cylinder and the stationary ring,
and that the extensions of the contact surfaces intersect each
other at or near a neutral point of thermal expansion of the
cylinder.
According to one embodiment of this invention, the upper and lower
guide rings are positioned above and below the stationary ring to
surround the cylinder and the inclined contact surfaces are formed
between the stationary ring and the guide rings.
According to a modified embodiment, one of the guide rings is
substituted by a radial flange provided for the cylinder on the
outer surface at one end thereof. The flange is formed with an
inclined surface that cooperates with a corresponding inclined
surface of the stationary ring thus forming said contact
surface.
According to still further modification of this invention, the
cylinder is provided with a plurality of radial projections and the
stationary ring is provided with a plurality of dove-tail shaped
grooves for accommodating the radial projections and the extensions
of the contact surfaces between the projections and the groove
intersect each other at or near the axis of the cylinder which
includes the neutral point.
In any embodiment, since the extensions of the contact surfaces
that permit relative movement of the cylinder and the stationary
ring intersect each other at or near a neutral point of thermal
expansion of the cylinder, when the cylinder and stationary ring
undergo thermal expansion, the cylinder and the stationary ring are
maintained always in an exact concentric relation notwithstanding
the fact that they are made of materials with different
coefficients of thermal expansion whereby the defects described
above can be obviated. Moreover as the end surface of the guide
ring or the stationary ring can be maintained in flush with the end
surface of the cylinder it is possible to prevent the molten metal
from reaching the contact surfaces.
This construction also simplifies construction of the pump and
reduces its cost of manufacturing.
BRIEF DESCRIPTION OF THE DRAWINGS
Further objects and advantages of the invention will be more fully
understood from the following detailed description taken in
conjunction with the accompanying drawings in which:
FIG. 1 is a sectional view of the injection pump embodying the
invention;
FIG. 2 is an enlarged partial sectional view of the cylinder,
piston and associated parts of the pump shown in FIG. 1;
FIGS 3a-3c show sectional views of various designs wherein the
guide rings and the stationary ring engage with each other at
different inclination angles;
FIGS 4A and 4B shows diagrams useful to explain the operations of
the designs shown in FIGS. 3b and 3c;
FIG. 5 is a sectional view of a modified cylinder;
FIG. 6 is a sectional view of the cylinder and the stationary ring
shown in FIG. 5 to show thermal deformations thereof and
FIG. 7 is a cross-sectional view of another modification of the
cylinder and the stationary ring.
DESCRIPTION OF THE PREFERRED EMBODIMENT
With reference to FIG. 1 of the accompanying drawings, a metal
melting furnace 1a containing molten metal 2 is mounted on a
pedestal 1 and an injection pump 3 embodying the invention is
immersed in the molten metal 2. Pump 3 is supported by a frame 8
extending above the furnace and secured to a stationary member 14a
of a die cast machine by means of bolts 9.
A cylinder 5 is disposed in the body 3a of the pump which is
immersed in the molten metal for receiving a piston or plunger 4a
secured to the lower end of a piston rod 4 which is connected via a
coupling 11 to a piston-cylinder assembly 10 secured to the upper
portion of the frame 8.
Between the outer surface of cylinder 5 and the inner surface of a
cylinder bore 5a are disposed two pairs of upper and lower guide
rings 6a and 6b and an intermediate stationary ring 6c, as best
shown in FIG. 2. In order to prevent the molten metal from
contacting upper and lower guide rings 6a and 6b, and stationary
ring 6c resilient sealing members 18 and 19 are urged against the
upper surface of the upper guide ring 6a and the lower surface of
the lower guide ring 6b by means of a cylindrical clamping member 7
with its upper end secured to frame 8 by means of bolts 7a.
A pressurizing chamber 12 for the molten metal 2 is formed in the
body 3a of the pump to extend between the lower portion of the
cylinder 5 and the left upper portion of the body. A hollow
coupling memmber 13a is secured to the left upper end of the
pressurizing chamber 12 to connect it with one end of a nozzle 13b
having spherical surfaces on the opposite ends thereof, the
opposite end of the nozzle 13b being in engagement with a metal
mould 14b of the die cast machine. When the frame 8 is secured to
stationary member 14a by tightening bolts 9 the opposite ends of
the nozzle 13b are tightly clamped between the mould 14b and the
coupling member 13a thus preventing leakage of the molten metal
2.
As shown in FIG. 2, piston 4a is secured to the lower end of piston
rod 4 by means of a bolt 4d extending through the piston 4a. The
upper end of bolt 4d is connected to the lower end of piston rod 4
by means of a transverse pin 4e to prevent relative rotation of
piston 4a and piston rod 4. Equally spaced apart grooves 15
extending from the bottom of piston 4a to an intermediate point
thereof are formed in the outer peripheral surface of piston 4a.
Accordingly, when the piston 4a is moved upwardly by the
piston-cylinder assembly 10, the molten metal 2 is permitted to
flow into the pressurizing chamber 12 through the grooves 15 as
shown by an arrow. An opening 7b is formed to extend through the
side walls of the cylindrical clamping member 7 for permitting the
molten metal to flow into the grooves 15 from outside.
Cylinder 5 is made of a material having high resistance to wear and
heat shock and a relatively small coefficient of thermal expansion,
ceramic for example, whereas guide rings 6a and 6b are made of a
material having substantially the same coefficient of thermal
expansion as cylinder 5, for example tungsten and molybdenum. The
stationary ring 6c is made of a material having substantially the
same coefficient of thermal expansion as the body 3a of the pump,
said coefficient of thermal expansion being larger than that of the
cylinder 5 and guide rings 6a and 6b.
Contacting surfaces between the upper and lower guide rings 6a and
6b and the stationary ring 6c are inclined with respect to the
horizontal. Extensions (shown by dot and dash lines) of these
inclined contact surfaces intersect at point Q on the axes of the
piston and cylinder, the point Q being the neutral or reference
point of thermal expansion of the cylinder 5; that is, the point at
which lines passing through the initial and final points of any
point of the cylinder 5 intersect when said any point displaces due
to thermal expansion when the cylinder 5 is heated to bring off its
points to the same temperature. So long as the apices of two cones
defined by the extensions of the inclined contact surfaces are
located near the reference point Q, the inclination angles of the
upper and lower contact surfaces will not necessarily be equal.
A resilient sealing ring 17 is interposed between the upper surface
of the body 3a of the pump and the lower surface of the cylindrical
clamping member 7 for preventing the molten metal from flowing into
the gap between the body 3a and upper and lower guide rings 6a and
6b and the stationary ring 6c.
FIGS. 3a, 3b and 3c are diagrams to explain the reason that the
upper and lower end surfaces of the cylinder 5 and the upper and
lower guide rings 6a and 6b become out of alignment due to the
difference in the thermal expansion of the cylinder 5, guide rings
6a and 6b and stationary ring 6c.
According to the design shown in FIG. 3a, the apex of the cone
defined by the extension of the contact surface between upper guide
ring 6a and the stationary ring 6c and that of the cone defined by
the extension of the contact surface between lower guide ring 6b
and the stationary guide ring 6c substantially coincide with each
other and these apices are located at or close to the neutral point
Q of the cylinder 5 so that due to thermal expansion a gap t.sub.2
will be formed between the inner surface of the stationary ring 6c
and the outer surface of cylinder 5 and gaps t.sub.1 will be formed
between the outer surfaces of guide rings 6a and 6b and the inner
surface of the cylinder bore 5a. The extensions of the contact
surfaces between stationary ring 6c and guide rings 6a and 6b
intersect at or near the neutral point Q. Since cylinder 5 and
guide rings 6a and 6b are made of materials having substantially
the same coefficient of thermal expansion the upper and lower
contact surfaces of the stationary ring 6c tend to expand outwardly
along lines l.sub.1 and l.sub.2 shown in FIG. 3A. As a result, the
end surfaces of the cylinder 5 and guide rings 6a and 6b always lie
in the same horizontal planes even when they undergo thermal
expansion.
In the design shown in FIG. 3B, the inclination angles of the
contact surfaces are made smaller than those of the design shown in
FIG. 3A. Thus the apices Q.sub.1 and Q.sub.2 of respective cones
are displaced upwardly and lowerwardly from the neutral point Q.
Consequently, upon thermal expansion the end surfaces of guide
rings 6a and 6b project by t.sub.3 beyond the end surface of the
cylinder 5.
In the design shown in FIG. 3c, the inclination angles of the
contact surfaces are made larger than those of the design shown in
FIG. 3A so that the apices Q.sub.1 and Q.sub.2 of the cones are
displaced downwardly and upwardly from the neutral point Q, and the
end surfaces of the guide rings 6a and 6b terminate at horizontal
planes shorter than the end surface of the cylinder 5 by t.sub.4.
However, it should be understood that distance t.sub.4 is not
caused by thermal expansion as distance t.sub.3 but caused by the
movement of guide rings 6a and 6b to fill the gaps formed between
the contact surfaces of the stationary ring 6c and guide rings 6a
and 6b as will be described later in more detail.
FIGS. 4A and 4B correspond to FIGS. 3B and 3C respectively and show
the relative positions of the guide ring 6a and the stationary ring
6c when they undergo thermal expansion. Thus, FIG. 4A shows a case
wherein the inclination of the contact surface is small and in
which the stationary ring 6c in contact with the guide ring 6a is
shown as a triangle 21. It is assumed that the apex 21a of the
triangle 21 is in contact with the lower surface of the guide ring
6a and a line interconnecting the apex 21a and the reference or
neutral point Q is designated by L.sub.Q. To simplify the
description it is assumed now that the thermal expansion of the
guide ring 6a is zero. Then, when the stationary ring 6c undergoes
thermal expansion, the triangle 21 moves toward right upper along
line L.sub.Q with the result that the contact surface of the guide
ring 6a is pushed upwardly as shown by dotted lines.
Where the inclination angle of the contact surface is large as
shown by FIG. 4B, the triangle will be shown by 21' and its apex
will move toward right upper along line L.sub.Q thereby forming a
gap t.sub.4 between the lower surface of guide ring 6a and the apex
of triangle 21'.
The invention described above has the following advantages.
1. Upon thermal expansion, although gaps t.sub.1 and t.sub.2 are
formed as shown in FIG. 3A, the guide rings 6a and 6b do not move
relative to cylinder 5 so that the end surfaces of the guide rings
6a and 6b are maintained always in the same horizontal plane as the
end surface of the cylinder 5 with the result that the molten metal
does not enter through the resilient sealing member.
2. The invention simplifies the configuration of the component
parts and allows for component parts other than the cylinder with
materials having higher workability than ceramics. For example,
guide ring 6a and 6b may be made of tungsten or molybdenum. As a
result, it is possible to use simple machine tools and cheap
materials, thus decreasing the cost of manufacturing of the
injection pump.
3. When the configuration of the cylinder, which is most expensive
to manufacture, becomes complex, its cost of manufacturing
increases greatly. For this reason, although many attempts have
been made in the past to solve the same problem as in this
invention they were proved to be unsatisfactory because of their
lower utility and economy. Furthermore, the cylinder is usually
made by a hot press process, so that when the cylinder is made to
have a configuration other than cylindrical, it is difficult to
make homogenous the hot pressed material, thus causing deformation
and fracture of the cylinder during use. According to this
invention, deformation of the peripheral portion of the cylinder
caused by thermal expansion is prevented by designing the cylinder
to have a cylindrical configuration and by obviating the adverse
effect caused by the thermal displacement of the peripheral portion
of the cylinder by causing the extension of the contact surfaces
between the guide rings and the stationary ring to interest each
other at or near the neutral point of the cylinder.
In a modification shown in FIGS. 5 and 6, the lower guide ring of
the foregoing embodiment is made integral with the cylinder. More
particularly, cylinder 5 made of ceramic material is formed with an
integral radial shoulder 20 about its lower end. The shoulder 20
corresponds to guide ring 6b of the previous embodiment and is
formed with an upwardly inclined surface S at its upper end. The
upper guide ring 23 is similar to guide ring 6a described above and
is disposed symmetrically with respect to shoulder 20. Extentions
of the inclined surfaces S and T of the shoulder 20 and guide ring
21 intersect each other at or near the neutral point Q on the axis
of the cylinder. A stationary ring 22, made of ferrous material for
example, has an inside configuration closely surrounding the outer
surfaces of cylinder 5, its shoulder 20 and guide ring 23.
Resilient sealing rings 24, 25 and 26 are provided to prevent the
molten metal from reaching the contact surface and are held in
position by means of a clamping ring 27 and bolts 28.
When heated, the cylinder 5 and stationary ring 22 expand in the
radial and axial directions about the neutral point Q. Due to the
difference in the coefficient of thermal expansion gaps t.sub.1 to
t.sub.2 are formed between the cylinder and the stationary ring. At
the same time, although contact surfaces between inclined surfaces
S and T and the cooperating surfaces of the stationary ring also
expand, no gap will be formed at these contact surfaces because
these cooperating surfaces expand in the same direction, whereby
the center axis of the cylinder will not be displaced.
In another embodiment is shown in FIG. 7, the contact or sliding
surfaces between the cylinder and the stationary ring extend in the
radial direction with respect to the center axis of the cylinder.
In this embodiment, cylinder 30 made of ceramic material is
provided with a plurality of integral radial projections 31 each
received in a dove-tail shaped axial groove 32 of stationary ring
34, made of ferrous metal for example. The contact or sliding
surfaces 33 of projections 31 and dove-tail grooves 32 extend in
the radial direction.
When heated, as the coefficients of thermal expansion of the
cylinder and the stationary ring are not equal, that is the thermal
expansion coefficient of the cylinder is smaller than that of the
stationary ring, there is a tendency of forming gaps g between the
outer surface of the cylinder and the inner surface of the
stationary ring. However, as the contact surfaces between these
members extend in the radial direction starting from the common
axis of the cylinder and the stationary ring which includes the
neutral point, these members are maintained always in the
concentric relation, thus preventing displacement of the axis of
the cylinder.
* * * * *