US3703853A

US3703853A - Compact fluid actuator and method of making it

Info

Publication number: US3703853A
Application number: US98775A
Authority: US
Inventors: Donald J Steger
Original assignee: International Business Machines Corp
Current assignee: International Business Machines Corp
Priority date: 1970-12-16
Filing date: 1970-12-16
Publication date: 1972-11-28
Anticipated expiration: 1989-11-28
Also published as: GB1309030A; DE2161646A1; FR2117856B1; JPS5237156B1; FR2117856A1

Abstract

A compact fluid powered actuator is constructed from a flexible tube assembled over a rigid core. The actuator includes an expansible chamber formed between the tube and the core. The chamber is bounded by naturally efficient and lowly stressed seals at the ends of the tube which tightly match the periphery of the core. This construction lends itself to mass production methods wherein a long core is assembled with a long tube enabling a plurality of actuators to be manufactured simultaneously.

Description

United States Patent Steger Nov. 28, 1972 COIVIPACT FLUID ACTUATOR AND 3,304,386 2/ 1967 Shlesinger ..200/83 METHOD OF MAKING IT 2,676,609 4/1954 Pfarrer ..92/92 3 006 306 10/ 1961 Pfeifier et a1. ..92/92 I [72] memo Dmm'd J stege" Cmmth Ky 3,051,143 8/1962 Nee ..92/92 [73] Assignee: International Business Machines Corporation, Armonk, Primary Examiner-Edgar W. Geoghegan 22 Filed: Dec. 16, 1970 f Attorney-Hamlin and Jancm and E. Ronald Coffman [21] Appl. No.: 98,775

[ ABSTRACT [52] US. Cl ..92/92, 92/91 A compact fluid powered actuator is constructed f [51] Int. Cl ..Folb 19/00 a flexible tube assembled over a rigid core The actua [58] Fleld of Search ..92/91, 92 tor incudes an expansible chamber formed between the tube and the core. The chamber is bounded by [56] References and naturally efficient and lowly stressed seals at the ends UNITED STATES PATENTS of the tube which tightly match the periphery of the core. This construction lends itself to mass production 2,612,909 lO/l952 Keller ..92/92 methods wherein a long core i assembled with a long 2,048,771 7/1936 Baldwin ..92/92 tube enabling a plurality f actuators to be manufac 2,991,763 7/1961 Marette ..121/48 med simultaneously 3,016,884 1/l962 Merriman ..121/48 3,048,121 8/1962 Sheesley 103/152 10 Claims, 8 Drawing Figures PATENTEUWZB SHEEI 1 OF 2 3103-853 FIG. 1

FIG. 2

FIG. 3

INVENTOR DONALD J. STEGER ATTORNEY COMPACT FLUID ACTUATOR AND METHOD OF MAKING IT BACKGROUND OF THE INVENTION Bellows, pistons and diaphragms have long been employed as expansible chamber actuators for converting pneumatic or hydraulic energy into an output force. A typical limitation on the use of actuators has been the cost and complexity of overcoming, or of living with, the problems of fluid sealing and in the case of a be]- lows or diaphragm, fracture of a flexible member.

Of these three traditional actuators, the bellows provides the greatest simplicity since it can be manufactured somewhat as a single member. The traditional bellows includes a plurality of so-called accordion pleats which enable a significant output stroke. The apex of each pleat has a small radius bend which is subject to failure upon repeated stressing. The bellows device, while mechanically simple due to its potential one piece construction, is rather complex from a manufacturing viewpoint particularly where small size bellows are concerned. In small size bellows the uniformity of wall thickness will determine the reliability of the bellows over a long period of time. Those skilled in the art familiar with the techniques for molding thin complex walls of flexible material and maintaining uniform wall thickness can recognize the limitations of the bellows actuator.

My invention employs the readily manufacturable shapes of a rigid cylinder and a flexible tube to minimize the sealing and flexure problem of an expansible chamber in a simple and highly effective manner. A tube press-fit over a cylinder of substantially equal periphery forms a natural or inherent seal which can be easily supplemented by a heat bond if desired. The reaction and support functions necessary to the actuator are compactly provided by the internal rigid core which lends itself to a simple snap-in frame mounting like that common to some fuses of similar shape. While the construction of the tube can be varied to some extent, I prefer to employ a relatively non-elastic material that is pre-formed into a bulge or extended surface portion defining the expansible chamber. Actuation of the device thus involves only flexural deformation rather than any significant amount of stretching. Due to the surrounding relationship of the tube with the cylindrical core, it is possible to restrict flexure to relatively large radii of curvature and thereby minimize the tendency for local failure that limits the potential success of a bellows type device.

While the actuator that l have invented has the capabilities indicated above which by themselves make it a desirable and highly effective device, it should be apparent that the simple shapes of tubes and cylinders can be manufactured to relatively close tolerances. Uniform wall thickness of a tube is relatively easy to obtain. Such uniformity is required to minimize stress concentrations that could cause localized failure. My actuator also lends itself to large quantity manufacture to minimize its basic cost. The fundamental shapes of a cylinder and a tube enable simultaneous construction of a plurality of expansible chambers on a long rod surrounded by a long tube. These devices can later be severed into a plurality.

These and other concepts, features, and advantages of my fluid actuator and the method of making it will be apparent to those skilled in the art from reading and understanding the following more specific illustrative embodiment of my invention wherein reference is made to the accompanying drawings, of which:

FIG. 1 is a perspective view of a fluid actuator constructed in accordance with my invention;

FIG. 2 is a longitudinal cross-sectional view of the actuator shown in FIG. 1 and taken along lines II II of FIG. 1;

FIG. 3 is a lateral or end cross-sectional view of the actuator shown in FIG. 1 taken along lines III III thereof;

FIG. 4 is a perspective view of the cylindrical core component of the actuator shown in FIG. 1;

FIG. 5 is a perspective view of the tubular component of the actuator shown in FIG. 1;

FIG. 6 is a somewhat schematic view showing a method of making the cylindrical core component of an actuator in accordance with my invention;

FIG. 7 is a schematic view showing a preferred method of forming the tubular component after assembly with the core component in accordance with my invention and FIG. 8 is a schematic manufacturing view showing the separation of a plurality of simultaneously formed devices into individual devices.

Referring now more specifically to the drawings, in FIGS. 1, 2, and 3 there is shown a compact fluid powered actuator or device 10 comprising a substantially rigid elongated core member 20 that is best seen in FIG. 4. Core member 20 is surrounded by a flexible relatively non-elastic, fluid impervious. tubular membrane or tube 30 that is best seen in FIG. 5. The tube 30 has a tubular axis 35 which is aligned with the axis 29 of the core member 20 when the two are assembled. The tube 30 includes an extended surface on bulge portion 31 that overlies an intermediately positioned recessed section 21 of the core member 20 to form an inflatable or expansible chamber 32. Fluid for inflating chamber 32 is supplied through a suitable conduit 1 l'within the core member 20. The fluid is transmitted through an inlet 22 and a longitudinal bore 23 to an elongated channel portion 23a where it is applied internally to the tube 30 to cause inflation of the chamber 32. Due to the inelastic character of tube 30, bulge portion 31 defines a fixed maximum volume for chamber 32 when inflated as shown in broken lines in FIG. 2.

An output or reaction member 40 is movably supported by a pivot axis or shaft 41 connected to a mounting bracket 42. As shown in broken lines in FIG. 2, output member 40 is driven upwardly upon inflation of the chamber 32. The mounting bracket 42 is secured to a frame part 43 by a screw 44 and includes a pair of spaced spring clip portions 45 for securely receiving the ends of the core member 20. It will be seen that upwardly turned portions 46 of the spring clip portions 45 will resiliently removably receive the core 20 in a manner similar to an elongated fuse mounting. Obviously other mounting devices can be employed with equal facility.

The details of the core member 20 are better shown in FIG. 4. The core member 20 is essentially of oblong cylindrical lateral cross-sectional or peripherial configurationr This cross-section, which is substantially uniform at opposite end sections 24 that are enlarged with respect to the recessed section 21; provides a flattened configuration having opposed primary surface portions 25 that provide a relatively large area compared to the side or secondary surface portions 26. The recessed section 21 has a longitudinal extent 27 that is long relative to the width 28 of the core member 20 thereby providing a relatively large potential surface area to lie in projection with the bulge portion 31 of the tube 30.

The recessed section 21 also has a surface configuration 21a that is made substantially complementary to the shape of a force receiving portion 47 of the output member 40. As best seen in FIG. 2, the force receiving portion 47 thus snuggly fits against the extended surface portion 31 of the tube 30 and rests against the complementary configured surface 21a (see FIG. 3) of the recessed portion 21 to define a stable end limit or rest position. Only a single layer of uncrimped membrane of the tube 30 lies between the force receiving portion 47 and the surface 21a, since as shown in FIG. 3, the excess material of the bulge portion 31 moves outwardly to the side where it does not interfere with the precise rest position of output member 40.

The core member 20 can be made of a variety of materials and by processes that include both molding and machining. If the core member 20 is made from stock material including the longitudinal bore 23 which extends throughout the entire length thereof, then a plug 23b must be provided to seal one end of the bore 23.

The tube 30, as shown in FIG. 5, has an internal periphery that is substantially equal to the external periphery of the core member end portions 24 to provide a tight fit therewith. It is preferable to employ a relatively non-elastic, but thermoplastic material in constructing the tube 30 to enable the molding of bulge 31 after the tube 30 has been mounted upon the core member 20. It will be recognized however that advantages remain even if an elastic membrane is employed without a pre-formed bulge 31.

The tube 30 is assembled with the core member 20 by moving the tube 30 along the longitudinal rectilinear axis of elongation 29 of the core member 20 and is inherently sealed therewith by the interference between the closely matching end portions 34 of the tube 30 and the end sections 24 of the core member 20. This inherent seal can be supplemented by thermoplastic bonding at 33 through the use of a heated tool or an ultrasonic device. Having assembled an inflatable device comprising the tube 30 mounted on the core member 20, the actuator is constructed simply by plugging this device into the mounting bracket 42 shown in FIG. 1.

The fundamentally simple and compatable shapes of a cylindrical core member and a tubular membrane enable efficient mass production of these actuators. As shown in FIG. 6, an elongated rod of stock material 50 provided with a longitudinally extending bore 51 is machined by a cutting tool 60 to provide a plurality of spaced recesses 52 which are separated by unmodified sections 53 therebetween. Having manufactured a core member with i a plurality of recessed sections 52 therein, a thermoplastic tubular membrane 54 is forced thereon with somewhat of a press fit. This elongated assembly then is placed in a mold 61 as shown in FIG. 7 containing a plurality of mold cavities each having a surface configuration 62 that defines the desired inflated shape of the bulge portion 31 (see FIGS. 2 and 5 Also the mold can contain heating devices 63 for bonding the tube 54 to the core sections 53. The tubular membrane 54 is heated prior to insertion in the mold to a temperature where it is thermoplastic. When the elongated heated assembly is placed in the mold 61 the membrane 54 is stretched by inflation through either the application of pressure to the bore 51 or by drawing a vacuum in the mold cavities 62. The stressed membrane thus permanently stretches to a shape defined by the mold cavity surface 62 and when colled will remain in this configuration. As shown in FIG. 8, the molded assembly is divided into individual fluid devices 55 by a cutter 64 and later can be finally processed to the specific configuration desired as shown in FIG. 1 for example.

Those skilled in the art will recognize that I have disclosed a uniquely simple but effective fluid actuator concept which can be embodied in a variety of materials and manufactured in a variety of ways. While a specific embodiment and a specific manufacturing method have been disclosed to enable those skilled in the art to understand and practice my invention, it is to be recognized that various modifications can be made without departing from the inventive concepts I have disclosed. Accordingly these concepts are to be limited only by the specific language of the appended claims.

I claim:

1. A compact fluid powered actuator comprising: a substantially rigid core member extending along an axis of elongation and having first and second relatively enlarged end sections positioned along said axis and separated by an intermediate recessed section and a bore that defines a fluid inlet intersecting said recessed section,

a flexible, fluid impervious elongated tubular membrane oriented so that its tubular axis extents along said core axis and passes through said core end sections, said membrane enveloping said core member at said recessed section and having first and second end portions that closely match and continuously sealingly encompass respective ones of said pair of opposed end sections to thereby define a substantially closed expansible chamber connected with said fluid inlet,

a reaction member positioned adjacent said membrane at said recessed section for receiving displacement force from said membrane upon introduction of fluid to said chamber through to said fluid inlet, and

means mounting said core member and said reaction member for relative movement therebetween.

2. An actuator as defined in claim 1 wherein said recessed section defines a surface configuration, and wherein said reaction member includes a force receiving portion contacting said membrane and having a surface configuration that is substantially complementary to said recessed section defined surface configuration.

3. An actuator as defined in claim 1 wherein said membrane is made of a relatively non-elastic material and has, at the region thereof that .overlies said recessed section, an extended surface portion defining an inflatable chamber having a predetermined fixed maximum volume.

4. An actuator as defined in claim 2 wherein said membrane is made of a relatively non-elastic material and has, at the region thereof that overlies said recessed section, an extended surface portion defining an inflatable chamber having a predetermined fixed maximum volume.

5. An actuator as defined in claim 1 wherein said membrane contacts the surface of said recessed section of said core member when fluid is not introduced into said fluid inlet and wherein the improvement further comprises:

an elongated channel formed in the surface of said recessed section and being extended in the direction of said core axis, said channel remaining at all times out of contact with said membrane and communicating with said bore for applying fluid introduced to said fluid inlet to a substantial area of said membrane.

6. An actuator as defined in claim 3 wherein said extended surface portion of said membrane contacts the surface of said recessed section of said core member when fluid is not introduced into said fluid inlet and wherein the improvement further comprises:

7. An actuator defined in claim 1 further comprising a mounting bracket attachable to a frame and means on said mounting bracket for removably receiving at least one of said end sections of said core member for supporting said core member in a substantially fixed position.

8. A compact fluid powered actuator comprising:

a substantially rigid core member extending along a rectilinear axis of elongation and having an oblong lateral cross-sectional configuration providing a pair of opposed primary surface portions having a substantially greater area than the remaining secondary surface portions, said core member further having a recessed section formed in one of said primary surface portions intermediate a pair of relatively enlarged opposed end sections, said recessed section being of a longitudinal extent that is substantially greater than its lateral extent, said core member further having a bore that defines a fluid inlet extending through one of said end sections and intersecting said recessed section,

flexible fluid impervious relatively non-elastic membrane having an extended surface position enveloping said core member at said recessed section to define an inflatable chamber having a predetermined fixed maximum volume, said membrane being sealingly received by each of said end sections, and

reaction member positioned adjacent said membrane at said recessed section for receiving displacement force from said membrane upon introduction of fluid to said fluid inlet, and

means mounting said core member and said reaction member for relative movement therebetween. 9. An actuator as defined 1n claim 8 wherein said recessed section defines a surface configuration, and wherein said reaction member includes a force receiving portion contacting said membrane and being shaped to be substantially complementary to said recessed section defined surface configuration.

10. An actuator as defined in claim 8 wherein said membrane contacts the surface of said recessed section of said core member when fluid is not introduced into said fluid inlet and wherein the improvement further comprises:

an elongated channel formed in the surface of said recessed section and being extended in the direction of said axis, said channel remaining at all times out of contact with said membrane and communicating with said bore for applying fluid introduced to said fluid inlet to a substantial area of said membrane.

Claims

1. A compact fluid powered actuator comprising: a substantially rigid core member extending along an axis of elongation and having first and second relatively enlarged end sections positioned along said axis and separated by an intermediate recessed section and a bore that defines a fluid inlet intersecting said recessed section, a flexible, fluid impervious elongated tubular membrane oriented so that its tubular axis extents along said core axis and passes through said core end sections, said membrane enveloping said core member at said recessed section and having first and second end portions that closely match and continuously sealingly encompass respective ones of said pair of opposed end sections to thereby define a substantially closed expansible chamber connected with said fluid inlet, a reaction member positioned adjacent said membrane at said recessed section for receiving displacement force from said membrane upon introduction of fluid to said chamber through to said fluid inlet, and means mounting said core member and said reaction member for relative movement therebetween.

3. An actuator as defined in claim 1 wherein said membrane is made of a relatively non-elastic material and has, at the region thereof that overlies said recessed section, an extended surface portion defining an inflatable chamber having a predetermined fixed maximum volume.

5. An actuator as defined in claim 1 wherein said membrane contacts the surface of said recessed section of said core member when fluid is not introduced into said fluid inlet and wherein the improvement further comprises: an elongated channel formed in the surface of said recessed section and being extended in the direction of said core axis, said channel remaining at all times out of contact with said membrane and communicating with said bore for applying fluid introduced to said fluid inlet to a substantial area of said membrane.

6. An actuator as defined in claim 3 wherein said extended surface portion of said membrane contacts the surface of said recessed section of said core member when fluid is not introduced into said fluid inlet and wherein the improvement further comprises: an elongated channel formed in the surface of said recessed section and being extended in the direction of said core axis, said channel remaining at all times out of contact with said membrane and communicating with said bore for applying fluid introduced to said fluid inlet to a substantial area of said membrane.

8. A compact fluid powered actuator comprising: a substantially rigid core member extending along a rectilinear axis of elongation and having an oblong lateral cross-sectional configuration providing a pair of opposed primary surface portions having a substantially greater area than the remaining secondary surface portions, said core member further having a recessed section formed in one of said primary surface portions intermediate a pair of relatively enlarged opposed end sections, said recessed section being of a longitudinal extent that is substantially greater than its lateral extent, said core member further having a bore that defines a fluid inlet extending through one of said end sections and intersecting said recessed section, a flexible fluid impervious relatively non-elastic membrane having an extended surface position enveloping said core member at said recessed section to define an inflatable chamber having a predetermined fixed maximum volume, said membrane being sealingly received by each of said end sections, and a reaction member positioned adjacent said membrane at said recessed section for receiving displacement force from said membrane upon introduction of fluid to said fluid inlet, and means mounting said core member and said reaction member for relative movement therebetween.

9. An actuator as defined in claim 8 wherein said recessed section defines a surface configuration, and wherein said reaction member includes a force receiving portion contacting said membrane and being shaped to be substantially complementary to said recessed section defined surface configuration.

10. An actuator as defined in claim 8 wherein said membrane contacts the surface of said recessed section of said core member when fluid is not introduced into said fluid inlet and wherein the improvement further comprises: an elongated channel formed in the surface of said recessed section and being extended in the direction of said axis, said channel remaining at all times out of contact with said membrane and communicating with said bore for applying fluid introduced to said fluid inlet to a substantial area of said membrane.