U.S. patent number 3,709,107 [Application Number 05/093,297] was granted by the patent office on 1973-01-09 for steel cylinder barrel having bonded bronze-iron valve plate.
This patent grant is currently assigned to General Signal Corporation. Invention is credited to Martin J. Alger, Jr., Nelson H. Dunn.
United States Patent |
3,709,107 |
Alger, Jr. , et al. |
January 9, 1973 |
STEEL CYLINDER BARREL HAVING BONDED BRONZE-IRON VALVE PLATE
Abstract
The disclosure concerns steel cylinder barrels for piston pumps
and motors having bonded non-steel valve plates. The valve plate
comprises a sintered iron powder matrix which is impregnated with
bronze and is metallurgically and mechanically bonded to one end of
the steel cylinder barrel. The valve plate is made from a porous
sintered iron blank which is mounted in contact with one end of a
steel barrel blank in an assembly which includes a mass of bronze
in the solid state. The assembly is heated in a non-oxidizing
atmosphere to a temperature between 1900.degree.F and 2000.degree.F
to melt the bronze and cause it to infiltrate the sintered valve
plate blank and bond to the steel. Thereafter, the assembly is
cooled in the non-oxidizing atmosphere to solidify the bronze,
followed by air cooling to room temperature. Finally, the finished
valve plate is machined from the bronze-impregnated sintered
preform.
Inventors: |
Alger, Jr.; Martin J.
(Watertown, NY), Dunn; Nelson H. (Watertown, NY) |
Assignee: |
General Signal Corporation
(N/A)
|
Family
ID: |
22238184 |
Appl.
No.: |
05/093,297 |
Filed: |
November 27, 1970 |
Current U.S.
Class: |
92/169.1;
428/553; 428/579; 428/923; 91/499; 428/567; 428/575; 428/677 |
Current CPC
Class: |
B22D
19/08 (20130101); F01B 3/0052 (20130101); Y10T
428/12215 (20150115); Y10T 428/1216 (20150115); Y10S
428/923 (20130101); Y10T 428/12063 (20150115); Y10T
428/12924 (20150115); Y10T 428/12243 (20150115) |
Current International
Class: |
F01B
3/00 (20060101); B22D 19/08 (20060101); F01b
011/02 () |
Field of
Search: |
;92/169 ;308/DIG.5,DIG.8
;29/149.5PM,182.1 ;75/28R |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
308,819 |
|
Feb 1930 |
|
GB |
|
751,649 |
|
Jul 1956 |
|
GB |
|
Primary Examiner: Kaufman; Milton
Assistant Examiner: Lazarus; Ronald H.
Claims
We claim:
1. A steel cylinder barrel for a piston pump or motor characterized
by a valve plate which comprises a sintered iron powder matrix
which is completely impregnated with bronze and is metallurgically
and mechanically bonded to an end face of the cylinder barrel,
there being an alloy of the constituents in the region of the
interface.
2. A cylinder barrel as defined in claim 1 in which the valve plate
comprises, by volume, 24 to 43 percent bronze.
3. A cylinder barrel as defined in claim 2 in which the valve plate
comprises, by volume, 27 to 29 percent bronze.
4. A cylinder barrel as defined in claim 1 in which the bronze
contains, by weight, 85% copper, 10% tin and 5% lead, and is free
of nickel.
5. A cylinder barrel as defined in claim 2 in which the bronze
contains, by weight, 85% copper, 10% tin and 5% lead, and is free
of nickel.
6. A cylinder barrel as defined in claim 3 in which the bronze
contains, by weight, 85% copper, 10% tin and 5% lead, and is free
of nickel.
7. A cylinder barrel as defined in claim 1 in which
a. the cylinder barrel contains a circular series of cylinder bores
which open through said end face; and
b. the valve plate has a series of integral projections which
extend into said bores, are metallurgically and mechanically bonded
to the bore walls, and each of which is pierced by a port.
Description
BACKGROUND AND SUMMARY OF THE INVENTION
In hydraulic pumps and motors of the rotary cylinder barrel,
longitudinally reciprocating piston type, oil usually is
transferred to and from the cylinder bores through a rotary valve
at one end of the cylinder barrel. This valve comprises a
stationary element containing arcuate high and low pressure ports
which angles slightly less than 180.degree., and an element which
rotates with the cylinder barrel and contains a circular series of
small arcuate ports, each of which communicates with one of the
cylinder bores in the barrel. Since the valving elements are in
continuous sliding engagement with each other during operation, it
is desirable, if not a practical necessity in the case of high
speed, high pressure hydraulic units, to make one of the two
elements of bronze. This arrangement can be incorporated in several
ways, but it is evident that the best approach for units which
employ steel cylinder barrels is to use a bronze rotary valving
element and to bond it directly to the end of the cylinder barrel.
However, use of this design has been limited by the lack of a
satisfactory process for producing a bond between the steel and the
bronze.
The object of this invention is to provide a practical and reliable
process for producing a valve plate which is intimately bonded to
the steel cylinder barrel, and which also provides a valve plate
having superior properties. According to the invention, the new
valve plate comprises a matrix of sintered iron powder which is
impregnated with bronze and is metallurgically and mechanically
bonded to the end of the steel cylinder barrel. This type of valve
plate affords an excellent bearing surface having greater strength
than the bronze and better bearing characteristics than the iron.
And, the intimate bond with the steel affords the absolute seal
against leakage and the resistance to errosion required in a high
performance pump or motor.
The process for making the new valve plate commences with the
formation of an assembly including a porous, sintered iron valve
plate blank, a steel cylinder barrel blank having an end face which
bears against the valve plate blank, and a charge of bronze in the
solid state having a volume sufficient to completely fill the pores
in the sintered iron blank. The assembly is heated in a
non-oxidizing atmosphere to a temperature between 1,900.degree.F
and 2,000.degree.F to melt the charge and cause the bronze to
infiltrate the valve plate blank and bond to the steel face of the
cylinder barrel blank. Thereafter, the assembly is cooled in the
controlled atmosphere to solidify the bronze, and then it is air
cooled to room temperature. Finally, the finished valve plate is
machined from the bronze-impregnated blank. The bond produced by
this process has a true metallurgical character inasmuch as the
region of the interface between the valve plate and the end face of
the cylinder barrel contains an alloy of the constituent
metals.
BRIEF DESCRIPTION OF THE DRAWING
The preferred embodiment of the invention and several alternatives
are described herein with reference to the accompanying drawing in
which:
FIG. 1 is a plan view of the blank-slug assembly.
FIG. 2 is a sectional view taken on line 2--2 of FIG. 1.
FIG. 3 is a sectional view taken on line 3--3 of FIG. 2.
FIG. 4 is an axial sectional view of the finished cylinder
barrel.
FIG. 5 is a face view of the finished valve plate shown in FIG.
4.
FIG. 6 is an axial sectional view of an alternative blank-slug
assembly.
DESCRIPTION OF THE EMBODIMENT OF FIGS. 1-5
The initial step of the preferred process concerns formation of the
assembly 11 (see FIGS. 1-3) which includes a steel cylinder barrel
blank 12, a sintered iron valve plate blank 13, a plurality of
bronze slugs 14, and a dry sand support 15. Cylinder barrel blank
12 is rough machined from SAE 52100, 1045 or 4150 steel stock and
is formed with a through axial bore 16, a circular series of
parallel cylinder bores 17, and a flat, annular end face 18. Face
18 is left in the rough turned state since surface irregularities
aid, rather than hinder, the bonding process. Moreover, it has been
found that the process is not adversely affected by the formation
of rust on face 18. After rough machining, blank 12 is cleaned to
remove chips and then vapor degreased. Degreasing is not essential
because any adherent oil and grease films will be burned off before
the bronze-steel bond is effected. However, since these volatiles
may leave a residue on face 18 which could cause localized
impairment of the bond, it is considered best to remove them
initially.
Valve plate blank 13 is a flat annulus having a thickness on the
order of 5/32 to 3/16 inch and provided around its periphery with a
series of uniformly spaced radial slots 19 which define the dynamic
pads 21 (see FIG. 5) of the finished article. It is centered with
respect to barrel blank 12 by a pair of sintered iron pins 22 which
extend through it and into the small diameter lower ends of two of
the bores 17. Blank 13 and pins 22 are made from the fine iron
powder normally used in the powdered metal industry and have a
density between 4.5 and 6.0 gms/cc, and preferably on the order of
5.6 to 5.8 gms/cc. In other words, these parts are porous, and,
based on a pure iron density of about 7.9 gms/cc, each includes 24
to 43 percent and preferably 27-29 percent voids. These voids are
distributed uniformly throughout the mass of each part and define
capillary passages which permit complete infiltration by molten
bronze. Except for their low density, blank 13 and pins 22 are
formed and sintered in the same manner as any conventional powdered
iron part.
The bronze slugs 14 are placed on the drill point surfaces at the
lower ends of the large diameter portions of bores 17 so that, when
melted, the bronze can flow downward onto valve plate blank 13. The
slugs are of uniform size and, in the aggregate, contain enough
bronze to completely fill the pores in blank 13 and pins 22.
Various bronzes can be used, but experience shows that the
composition should be free of zinc and nickel because these metals
tend to separate from the other constituents and form a brittle
interface which may crack under the service conditions encountered
by the completed cylinder barrel. The composition should also have
as low a lead content as possible because this metal will "bleed
out" during heat treatment of the driving splines of the finished
cylinder barrel. Bronzes having the following compositions, by
weight, have proven acceptable:
a. 80% copper, 10% tin, 10% lead
b. 89% copper, 11% tin
c. 90% copper, 10% tin
However, the preferred slugs 14 are made of a bronze containing 85
percent copper, 10 percent tin and 5 percent lead which is
purchased commercially in the nickel-free form. Although the slugs
may be bronze castings, it is considered better to use sintered
masses of bronze powder because this permits better control of
composition.
After assembly 11 has been completed, it is placed in a furnace and
supported in the illustrated upright position. The furnace should
contain a non-oxidizing atmosphere, such as the filtered natural
gas product commonly employed to control decarburization of the
steel in blank 12 during heat treatment, and, in a typical case, it
would be at a temperature of about 1,600.degree.F at the time
assembly 11 is introduced. Furnace temperature is then raised to an
elevated level above the melting range of the bronze and held there
long enough to insure that all parts of assembly 11 reach a
temperature which will produce a good metallurgical bond between
the bronze and the steel. Although bonding can be effected at an
assembly temperature on the order of 1,900.degree.F, experience
indicates that a temperature of 1,950.degree.F is needed in order
to provide the degree of bonding reliability required for a
production process. The furnace temperature and length of time this
temperature must be maintained in order to achieve the required
assembly temperature must be determined empirically because these
factors vary with furnace design and loading, i.e., the number of
assemblies 11 being processed at the same time. The final selection
involves a compromise since higher temperatures shorten holding
time but also cause excessive evaporation of bronze and, because of
localized hot spots, involve some risk of melting portions of steel
blank 12. Our studies show that furnace temperature above
2,000.degree.F are too risky and are not really demanded by
practical production considerations. For example, using a standard
heat-treating furnace capable of holding thirty assemblies 11, we
found that acceptable bonds were produced reliably at a furnace
temperature of 1,990.degree.F which was maintained for one
hour.
During the heating cycle just mentioned, the slugs 14 melt, and the
molten bronze either migrates into blank 13 through sintered iron
pins 22 or flows directly onto the blank through the open bores 17.
In any case, this metal is distributed throughout the mass of blank
13 by capillary action. The combined effects of the heat and the
infiltration renders the blank 13 somewhat plastic; therefore, the
weight of steel blank 12 is sufficient to cause blank 13 to conform
to any irregularities in the face 18. As a result, the bronze which
wets the upper face of blank 13 can migrate into and form a true
metallurgical and a mechanical bond with the steel over the entire
interface between the two blanks.
At the end of the heating cycle, i.e., after all parts of assembly
11 have reached the selected bonding temperature, the furnace is
allowed to cool so that the temperature of assembly 11 reduces
below the melting range of the bronze. Typically, this phase of the
process consumes one hour, furnace temperature decreases to about
1,400.degree.F, and the temperature of assembly 11 drops to a level
below 1,500.degree.F. These conditions insure solidification of the
bronze and permit opening of the furnace without risk of explosion
of the controlled atmosphere. Therefore, assembly 11 is now removed
from the furnace and allowed to air cool to room temperature. When
the bonded blanks 12 and 13 have cooled sufficiently, they are
removed from sand bend 15, sand blasted, and then transformed into
the finished cylinder barrel shown in FIGS. 4 and 5. The finishing
steps include:
1. Machining the inner and outer peripheral surfaces 23 and 24,
respectively, and the front face 25.
2. Cutting and heat treating driving splines 26.
3. Boring and honing cylinder bores 27, and end milling the arcuate
port 28 at the valve plate end of each bore.
4. Machining bonded valve plate 29 to form land 31.
5. Grinding and lapping the faces of dynamic pads 21 and land
31.
Although the foregoing description treats only the process steps of
the invention, it should be understood that, in the complete
commercial process, bonding of valve plate 29 is effected
simultaneously with the cylinder liner bonding step of our
application Ser. No. 93,130, or Ser. No. 93,298, both filed
concurrently herewith.
DESCRIPTION OF THE FIG. 6 EMBODIMENT
It will be noticed in FIG. 4, that a portion of the arcuate port 28
at the end of each cylinder bore 27 is formed in the barrel blank
12, and therefore is surrounded by a steel web. The strength
afforded by this arrangement is needed in high performance pumps
which operate continuously at pressures on the order of 5,000
p.s.i. and at speeds around 4,000 r.p.m. However, in the case of
low performance units, e.g., those which operate at pressures of
1,500-2000 p.s.i. and at speeds below 3,000 r.p.m., real advantages
can be realized by eliminating the steel web. The assembly 11a
shown in FIG. 6 may be used for producing cylinder barrels for this
type of service.
As shown in FIG. 6, the bores 17a are drilled through barrel blank
12a with a constant diameter, and the sintered iron valve plate
blank 13a is formed with a series of integral circular projections
32 which fit into the bores 17a and contain the arcuate ports 28a.
This design offers the important advantages that it eliminates
step-drilling of bores 17a and end milling of the arcuate ports
28a. The blanks 12a and 13a are bonded together in exactly the same
way as in the embodiment of FIGS. 1-5, but here, a bond is also
effected between the projections 32 and the wall of bore 17a.
The assembly 11a of FIG. 6 also is designed to effect simultaneous
bonding of bronze-iron liners in the bores 17a in accordance with
the teachings of application Ser. No. 92,298, mentioned above. For
this purpose, each bore is equipped with a porous sintered iron
sleeve 33 and a charge 34 of bronze of sufficient size to effect
complete impregnation of the sleeve. The lower end of each sleeve
33 abuts the face of the associated projection 32, so, during the
bonding operations, these parts will be intimately joined. This is
an added advantage because, as study of FIG. 6 will show, the
arrangement affords a lined and faced cylinder barrel in which all
contact between high pressure oil and the bronze-steel interfaces
is precluded. Thus, the design affords even better insurance
against leakage than the prior proposal of U.S. Pat. 3,169,488,
granted Feb. 16, 1965.
* * * * *