US3512908A - Vane construction for pneumatic device - Google Patents

Description

y 9, 1970 s. K. SMQTH 3,512,908

VANE CONSTRUCTION FOR PNEUMATIC DEVICE Filed Sept. 16, 1968 FIG. 2

63 6| FIG. 48 FIG. 4A PRIOR ART IMPROVEMENT 55 4 l!AlI INVENTOR STANLEY K. SMITH ATTORNEY United States Patent O M VANE CONSTRUCTION FOR PNEUMATIC DEVICE Stanley K. Smith, Baltimore, Md., assignor to The Black and Decker Manufacturing Company, Towson, Md.,

a corporation of Maryland Filed Sept. 16, 1968, Ser. No. 760,013 Int. Cl. F04c 1/00; F01c 1/00; F04h 21/08 U.S. Cl. 418-179 1 Claim ABSTRACT OF THE DISCLOSURE The device disclosed herein is a portable, rotary-type fluid handling device, such as a pump, motor or the like, which includes a generally cylindrical casing having a rotor rotatably supported therein. One or more vanes are slidably carried by the rotor and during rotation of the latter slide around the inner surface of the casing. Fluid inlet and outlet openings are formed in the casing for fluid entry and discharge during use of the device.

SUMMARY OF THE INVENTION The present invention deals specifically with a novel vane construction for use in and in combination with a rotary, fluid handling, pump, motor and the like. The vane is constructed of a formable, synthetic material and has embedded therein elongated fibers constructed of graphite or alumina which extend in a direction longitudinally of the vane. This construction contributes significantly to the life and performance of the vanes and greatly enhances the elliciency of the overall device by increasing dimensional stability, reducing friction and extending tool life.

Main objects of the present invention, therefore, are to provide a novel rotor vane construction for use in and in combination with a fluid handling device such as a pump, motor and the like, which construction enhances vane life and efficiency of the device.

Further objects of the invention are to provide a vane construction of the above character which is relatively inexpensive to manufacture, rugged in construction and reliable in use.

Other objects and advantages of the invention will be come more apparent from a consideration of the detailed description to follow taken in conjunction with the drawings annexed hereto.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevational view, partly broken away, illustrating a fluid operated tool embodying the present invention;

FIG. 2 is an enlarged view of a portion of FIG. 1 and with the vane partly broken away to illustrate one form of the invention;

FIG. 3 is an enlarged sectional view of a portion of FIG. 2 taken along the line 3-3 thereof;

FIG. 4A is an enlarged view of a portion of FIG. 2 and illustrating the clearance between moving and sta tionary parts made possible by the present invention;

FIG. 4B is a view similar to FIG. 4A and illustrating the necessary clearance in some prior art constructions; and

FIG. 5 is a view similar to FIG. 3 illustrating a laminated vane construction.

BROAD STATEMENT OF THE INVENTION Broadly described, the present invention relates to a fluid handling device including the combination of a stationary cylinder having respective end plate means, a rotor rotatable within the cylinder axially between the end plate means, said rotor having at least one radial slot formed therein, a vane freely mounted for radial sliding move- Patented May 19, 1970 ment in said slot, whereby said vane has a longitudinal edge in sliding engagement with the cylinder, said vane having generally parallel side edges at either end of said longitudinal edge and spaced apart a distance slightly less than said end plate means thereby defining clearance between said vane and end plate means; the improvement wherein said vane is constructed of a synthetic formable material having superimposed layers of woven cloth material embedded therein, said cloth material including threads extending only in a direction generally parallel to said longitudinal edge and generally perpendicular to said side edges and formed of a material selected from the group consisting of graphite and alumina, said cloth material further including threads extending in a direction generally perpendicular to said longitudinal edge and generally parallel to said transverse edges and formed of a material selected from the group consisting of wool, cotton, linen and mixtures thereof, rayon, nylon, Orlon and acrylic fibers, whereby said vane has improved dimensional stability in the longitudinal direction, whereby the coefficient of friction of said longitudinal edge is minimized, and whereby the longitudinal clearance with the respective end plate means is minimized for reduced air consumption and improved motor efliciency.

In another aspect, the present invention relates to a vane for use in a rotary fluid handling pump, motor and the like, said vane comprising an elongated flat member having a generally straight, longitudinal edge and a pair of generally straight, transverse edges, said member including a body of synthetic, fabricated material having elongated threads embedded therein, said threads including threads extending only in a direction generally parallel to said longitudinal edge and generally perpendicular to said transverse edges and constructed of a material selected rom the group consisting of graphite and alumina, whereby said vane has improved dimensional stability in the longitudinal direction and the coefficient of friction of said longitudinal edgeis minimized.

DETAILED DESCRIPTION Referring now specifically to the drawings, a rotary, pneumatic power tool, which is one type of device to which the present invention applies, is illustrated generally at 11 in FIG. 1. However, it is to be understood that this is for purposes of illustration only and that the present invention has application to the broad class of fluid handling pumps, motors and the like and whether they be portable or stationary.

With this in mind, the tool 11 is seen to include a motor housing 13 having a pistol-grip type handle 15 integral therewith or otherwise suitably secured thereto. A pneumatic motor 17 is positioned within the motor housing 13 and is powered by compressed air supplied thereto from a source through a suitable inlet conduit 19 at the handle 15. Delivery of compressed air to the motor 17 is controlled by conventional valving (not shown) located within the handle 15 and which, in turn, is controlled by a trigger 21 mounted on the handle 15. The details of the valving (not shown) and the interrelation of the trigger 21 therewith have been omitted here since they form no part of the present invention and since they are well within the scope of the skilled engineer.

The illustrated pneumatic motor 17 is of the type having a hollow, stationary cylinder 23 secured within the motor housing 13 and with its longitudinal, central axis extending longitudinally of the housing. The cylinder 23 has a cylindrical, inner surface 25 and its fore and aft ends are closed by end plates 27, 29 suitably secured thereto. A rotor 31 is disposed within the cylinder 23 and between the end plates 27, 29 and aligned stub shafts 33, 35 which extend through aligned openings 37, 39 in the end plates 27, 29, respectively, and are journaled in suitable fashion,

for example, by bearings (not shown) carried by the end plates 27, 29. The axis of the stud shafts 33, 35 is radially offset relative to the longitudinal axis of the cylinder 23 so that the rotor 31 rotates eccentrically relative to the axis of the cylinder 23.

The end plates 29, 27, or preferably the cylinder 23, are provided with suitable inlet and discharge opening means (not shown) communicated with the stator interior and with the valving (not shown) for the delivery and discharge of compressed air to and from the motor 17 Again, this construction is not illustrated nor described further here since it forms no part of the present invention and since it is fully within the realm of the skilled engineer.

The rotor 31 is formed with one or more radial slots 41 which extend the full axial length of the rotor 31 between the end plates 27, 29. As shown in FIG. 2, the slots 41 may be concavely curved along their radial inward end 43 while the end plates 27, 29 have straight, generally radially extending faces 45, 47, respectively, which define the lateral ends of the slots 41. A vane 49 is disposed within each of the rotor slots 41 and is adapted to slide radially thereof during rotor rotation. The vanes 49 (if more than one is used) are identical and each includes an elongated, flat body having a longitudinal, straight edge 51 adapted to ride around the cylinder surface and bounded by parallel, straight, lateral side edges 53, 55 which are slidable adjacent the end plate surfaces 45, 47, respectively. An inner, generally convex edge 57 on each vane 49 is generally complementary to and disposed opposite the associated slot inner end 43.

During use, compressed air is admitted to the cylinder 23 and bears against the vane or vanes 49 causing the rotor 31 to turn about the axis of the stub shafts 33, while centrifugal force causes the vane or vanes 49 to slide radially outwardly in their respective slots 41. This, in turn, causes the longitudinal edge 51 of each vane 49 to remain in sliding contact with the cylinder surface 25. The side edges 53, of each vane 49 are spaced apart a distance equal to the vane length and this dimension is selected to provide a predetermined clearance relative to the end plate surfaces 45, 47.

Many prior art vanes are constructed using laminated plastic materials selected from that group which has good shock and wear resistance as well as low moisture absorption characteristics. These vanes also generally employ a woven cloth constructed of organic or synthetic fibrous yarn, such as, for example, linen, cotton, wool or mixtures thereof, nylon, rayon, Orlon or acrylic material embedded in one or more layers of the laminated plastic to enhance its shock, and wear resistance together with its resistance to fracture.

These organic or synthetic fiber cloth reinforced vanes, however, have the detracting feature of being somewhat dimensionally unstable because of the moisture absorbing characteristics of these fibrous cloths. Thus, moisture in the device (either the fluid itself or moisture carried thereby) causes the cloth fibers and the vanes to elongate in the direction of fiber length. In the radial or transverse direction, this elongation may not be objectionable. However, the expectation of vane elongation in the axial or longitudinal direction requires that sufficient clearance be provided between the end plate faces 45, 47 and the vane edges 53, 55 to prevent the vanes 49 from hanging up during motor operation. It will be appreciated then that under conditions when the vane reinforcing fibers are less than saturated, excess clearance exists between the vane edges 53, 5S and end plate faces 45, 47 and the power and efficiency of the device is impaired.

In an effort to overcome this problem, a novel vane construction disclosed in the copending application of William S. Brucker, Ser. No. 575,887, filed Aug. 29, 1966, now Pat. No. 3,417,664, issued Dec. 24, 1968, and owned by the assignee of the present application has been developed. There, a vane construction embodying reinforcing threads extending in a direction longitudinally of the vane and formed of a relatively hard material having low moisture absorbing and low coefficient of friction properties, e.g., glass fiber, was disclosed. This novel vane construction provides the desired dimensional stability characteristics so that with this vane, clearance between the vane edges 53, 55 and the end plate faces 45, 47 is minimized.

In addition, some of these longitudinally extending threads become exposed at the vane edge 51 as the synthetic vane material wears away. Thus, these threads (e.g. glass fiber) facilitate higher rotor speeds and increased output for the reason of the low coefficient of friction provided by these threads and because this relatively hard material polishes the cylinder surface 25 reducing its coefficient of friction and pressure losses therepast. Furthermore, the lower friction achieved by this construction produces less heat in the device and increases the expected vane life. All in all, the invention disclosed in the Brucker application has made a significant contribution to the field of rotary, vane-type fluid handling devices.

In the present application, a similarly formed vane embodying a body of synthetic, fabricated material having reinforcing threads constructed from a material selected frm the group consisting of alumina and graphite is disclosed. Thus, it has been discovered that a vane reinforced with alumina or graphite threads embedded therein and extending in a longitudinal direction possesses highly desirable dimensional stability and low friction characteristics. In addition, these longitudinally extending, alumina or graphite threads polish the cylinder surface 25 during use and enhance the efficiency and reduce the losses of the device in which it is used.

Thus, as shown in FIGS. 2 and 3, the vane 49 comprises an elongated body of synthetic, fabricated material having embedded therein reinforcing threads 59 constructed of alumina or graphite which extend in an axial or longitudinal direction. For ease of fabrication, these threads 59 are interwoven in cloth-like fashion with other threads 61 which extend radially or transversely of the vane 49. Desirably, these threads 61 are relatively soft, so as not to gouge the cylinder wall 25, and are moisture absorbing so that the synthetic, fabricated vane material will adhere thereto. A material selected from the group consisting of linen, cotton, wool and mixtures thereof, nylon, rayon, Orlon and acrylic fibers is satisfactory for these threads 61 even though these materials will expand with moisture absorption since radial elongation of the vane 49 may not be objectionable.

It will be appreciated that the woven cloth embedded in the vane body increases the resistance of the vane to shear or fracture under shock loading. The longitudinal threads 59 are substantially non-moisture absorbing while the transverse threads 61 are highly moisture absorbent. This makes the vane strength greater in planes parallel to the longitudinal edge 51 than in p anes perpendicular thereto. However, the primary shock loads on the vane 49 occur when the vanes rock in an arcuate direction within their slots 41 and are thrown against the outer radial edges of the slots 41. These loads develop stresses in planes parallel to the edge 51 which is the direction in which the vanes 49' have their greatest strength.

It will be appreciated that in some cases it may be desirable to provide greater strength in the vane along planes normal to the vane edge 51. In these cases, it may be possible to substitute threads made of material selected from the group described above for threads 61 for some of the longitudinal alumina or graphite threads 59. The substituted threads are more absorbent and provide a stronger bond to the synthetic fabricated vane material thereby increasing the strength of the vane along planes running transverse thereto. The remaining alumina or graphite threads 59 are substantially non-absorbent and therefore provide greater dimensional stability than would be attained without them. In addition, the remaining alumina or graphite threads 59 also contribute to lowering the coefficient of friction and increasing the hardness of the vane edge 51 as these threads become exposed along this edge.

The vane construction disclosed is readily formed using known and conventional manufacturing techniques. Thus, for example, the threads 59, 61 may be woven, using known weaving techniques, and passed through a bath of the synthetic, formable vane material in liquid form. The non-absorbent threads 59 are coated with this material while the threads 61 are impregnated thereby and the treated cloth is then passed through calender-type rolls which apply a relatively thick layer of the synthetic material, e.g., thermosetting resin, thereto. The resulting product, shown in FIG. 3, may then be dried but is not allowed to set. Thereafter, one, or if desired, several superimposed layers of this material are placed in a hydraulic press and are heated to the final curing temperature of the synthetic material. If a plurality of superimposed sheets are molded, a construction such as that shown at 63 in FIG. is formed. In either case, the formed sheet can then be cut to size employing known techniques to form the vanes 49. In the event only the longitudinal threads 59 are employed, they are treated and coated in the same way except that a different mechanism, adapted to handle these unwoven threads, need be employed.

With reference now to FIGS. 4A and 4B, a comparison between the required initial axial or longitudinal clearance between the rotor vane transverse edge 55 and the end plate surface 47 of the present invention and that of the prior art is illustrated. In vanes using longitudinal threads constructed or moisture absorbing material such as linen, cotton, wool or mixtures thereof, nylon, Orlon, rayon or acrylic fibers, an initial clearance which is a function of the vane length and the coefficient of expansion of the particular longitudinal thread, fiber material. This initial clearance is represented at B in FIG. 4B. In the present invention where the longitudinal threads 59 are constructed from alumina or graphite, an initial clearance represented at A in FIG. 4A is required which substantially is only that clearance necessary to prevent excessive friction between the vane 49 and the end plate faces 45, 47. In the prior art constructions described, a clearance A was reached only when the longitudinal fibers were substantially completed saturated so that prior to this saturated condition, sub stantial power losses were sustained.

By the foregoing, there has been disclosed a novel vane construction calculated to fulfill the inventive objects hereinabove set forth, and while a preferred embodiment of the present invention has been illustrated and described in detail, various additions, substitutions, modifications and omissions may be made thereto without departing from the spirit of the invention as encompassed by the appended claim.

I claim:

1. In a fluid handling device including the combination of a. stationary cylinder having respective end plate means, a rotor rotatable within the cylinder axially between the end plate means, said rotor having at least one radial slot formed therein, a vane freely mounted for radial; sliding movement in said slot, whereby said vane has a longitudinal edge in sliding engagement with said cylinder, said vane having generally parallel side edges at either end of said longitudinal edge and spaced apart a distance slightly less than said end plate means thereby defining clearance between said vane and end plate means; the improvement wherein said vane is constructed of synthetic formable material having superimposed layers of woven cloth material embedded therein, said cloth material including threads extending only in a direction generally parallel to said longitudinal edge and generally perpendicular to said side edges and formed of a material selected from the group consisting of graphite and alumina, said cloth material further including threads extending a direction generally perepndicular to said longitudinal edge and generally parallel to said transverse edges and formed of a material selected from the group consisting of wool, cotton, linen and mixtures thereof, rayon, nylon, Orlon and acrylic fibers, whereby said vane has improved dimensional stability in the longitudinal direction, whereby the coefficient of friction of said longitudinal edge is minimized, and whereby the longitudinal clearance with the respective end plate means is minimized for reduced air consumption and improved motor efficiency.

References Cited UNITED STATES PATENTS 3,107,152 10/1963 Ford et al 308 3,116,975 1/1964 Cross at al. 3,151,015 9/1964 Griffith 308-238 3,417,664 12/1966 Brucker 103-216 HENRY F. RADUAZO, Primary Examiner US. Cl. X.R.

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