US3417664A - Vane construction for pneumatic motor - Google Patents

Description

Dec. 24, 1968 w. s. BRUCKER 3,417,664

VANE CONSTRUCTION FOR PNEUMATIC MOTOR Filed Aug. 29, 1966 GLASS FIBERS (LONGITUDINALLY) \\\K -t.\\ LINEN THREADS \\5\\ 1\*&\\'.\\\'\ RESIN 59 (RADIALLY) 57 55 FIG.4B FIG. 4A

PRIOR ART 23 IMPROVEMENT 23 P CLEARANCE "A" INVENTOR WILLIAM S. BRUCKER ATTORNEY United States Patent 3,417,664 VANE CONSTRUCTION FOR PNEUMATIC MOTOR William S. Brucker, Towson, Md., assignor to The Black and Decker Manufacturing Company, Towson, Md., a corporation of Maryland Filed Aug. 29, 1966, Ser. No. 575,887 8 Claims. (Cl. 91119) ABSTRACT OF THE DISCLOSURE The device disclosed is a portable, power tool having a pneumatic motor which includes a rotor and stator. The rotor has a plurality of radially movable vanes each of which is reinforced with relatively hard, low moisture absorbing, low expansion threads extending in a direction longitudinally of the vane and axially of the motor.

This invention relates generally to pneumatic devices, and particularly to an improved vane construction for pneumatic motors.

Important objects of the present invention are to provide an improved pneumatic motor vane construction possessing high dimensional stability and operational strength characteristics and one which is adapted to provide high motor efi'lciency during use.

A more particular important object of the present invention is to provide an improved, pneumatic motor vane construction of the above character which effectively eliminates dimensional change in a desired direction during use and therefore permits closer manufacturing tolerances and less clearance between the vanes and the pneumatic motor end plate components.

Another object of the present invention is to provide an improved motor vane construction of the above character which permits use of standard manufacturing techniques in the formation thereof.

Further objects of the present invention include an improved pneumatic motor vane construction of the above character which is relatively inexpensive to manufacture, durable in construction and reliable in use.

Other objects and advantages of the present invention will become more apparent [from a consideration of the following detailed description taken in conjunction with the drawings in which:

FIG. 1 is an elevational view, partly in section, illustrating a typical form of portable power tool embodying the present invention;

FIG. 2 is an enlarged fragmentary sectional view, partly broken away, illustrating the novel vane construction of the present invention;

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

FIG. 4A is an enlarged view of a portion of FIG. 2 taken within the enclosure 4 thereof and illustrating the clearance between moving and stationary parts made possible by the present invention;

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

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

Broadly described, the present invention relates to a pneumatic motor including the combination of a stator having respective end plate means, a rotor journaled within the stator 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 the slot, whereby said vane has a longitudinal edge in sliding engagement with the stator and further has respective side edges, at least one of which side edges has a longiice tudinal clearance with a respective one of the end plate means, said vane having a reinforcing cloth embedded therein, said cloth comprising interwoven threads including longitudinal and radial threads, only said longitudinal threads including threads being formed of a relatively hard material having relatively low moisture absorbing properties with a consonant relatively low coefiicient of expansion, whereby said vane has improved dimensional stability in the longitudinal direction, whereby the coeflicient 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 includes a pneumatic motor vane comprising an elongated frame member having a generally straight, longitudinal edge and a pair of generally straight, transverse edges, said member having elongated threads embedded in a body of synthetic fabricated material, said threads including threads formed of a relatively hard material having relatively low moisture absorbing properties with a consonant relatively low coeflicient of expansion which extend only in a direction generally parallel to said longitudinal edge, whereby to minimize the coefficient of friction of said vane longitudinal edge and maximize the longitudinal dimensional stability of said vane.

Referring now more specifically to the drawings, a typical rotary power tool, for example, an impact wrench, embodying the present invention is illustratedgenerally at 11 in FIG. 1 and 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, partially illustrated at 17, is positioned within the motor housing 13 and is motivated by compressed air supplied thereto from a source through a suitable inlet conduit 19 extending through the handle 15. Delivery of compressed air to the motor 17 is controlled by conventional valving (not shown) which may be located within the handle 15 or the motor housing 13 and which valving, in turn, is controlled by manipulation of a trigger 21 mounted on the handle 15. The valving and trigger control employed may be any one of a number of conventional arrangements well within the realm of the skilled engineer and since this structure forms no part of the present invention, it has not been illustrated and is not described in further detail here.

The pneumatic motor 17 preferably is of the type having a hollow, generally cylindrical stator 23 secured within the motor housing 13 and having its longitudinal, central axis extending longitudinally of the housing. The stator 23 has a cylindrical inner surface 24 and the fore and aft ends of the stator 23 are closed by end plates 25, 27 which may be removably secured to the stator 23 in suitable fashion. The end plates 25, 27 are provided with aligned openings 29, 31 adapted to receive stub shafts 33, 35 formed centrally on the fore and aft ends, respectively, of a rotor 37. The axis of the openings 29, 31 is radially offset relative to the axis of the stator 23 so that the rotor 37 rotates eccentrically relative to the axis of the stator 23. The end plates 25, 27 preferably carry bearings (not shown) to support the rotor shafts 33, 35 for free rotation.

The end plate 27 preferably is provided with suitable inlet opening means (not shown) communicated with the stator interior and with the valving (not shown) through which compressed air is delivered. End plates having inlet opening means of this type are well known in the art of pneumatic motors; for example, reference may be made to the US. patent to Egon Zizka, No. 3,080,851, granted Mar. 12, 1963 and owned by the assignee of the present application for a better understanding thereof,

as well as for an understanding of the rotor support construction.

As is customary, the rotor 37 is formed with a plurality of angularly spaced, axially extending slots 39 which extend the length of the rotor between the stub shaft portions 33, 35. The slots 39 are convexly curved along their radial inward end 41 and the end plates 25, 27 have straight, generally radially extending faces 43, 45 which define the lateral ends of the slots 39. A novel vane 47 is disposed within each of the slots 39 and is adapted to slide radially thereof during rotor rotation. The vanes 47 are identical and each has a pair of straight, parallel, lateral side edges 49, 51 slidable adjacent the end plate surfaces 43, 45, respectively, and an inner convex edge 53 shaped complementary to the slot surface 41. An outer, fiat edge 55 on each vane 47 is adapted to engage the inner surface 24 of the stator 23.

As described, the vanes 47 are slidable within the rotor slots 39 and during rotor rotation the vanes move radially outwardly under centrifugal force. This maintains each vane 47 with its outer edge 55 engaging the stator surface 24 so that compressed air admitted to the stator 23 bears against the vanes 47 and turns the rotor 37.

In the past, it has been customary to form the vanes from various types of laminated plastic materials which are selected from those having good shock and Wear resistance and low moisture absorption characteristics. In addition, 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 is often embedded in one or more layers of the laminated plastic to further increase its shock and wear resistance as well as its resistance to fracture during use. However, while the organic or synthetic fibrous cloth adds to the vane strength, it also detracts from the dimensional stability thereof because of its inherent moisture absorption characteristics and the resultant tendency thereof to elongate as more moisture is absorbed thereby.

The compressed air delivered to the motor 17 carries moisture with it. The organic or synthetic fibrous yarns absorb this moisture with the result that these yarns and therefore the vanes elongate both longitudinally and transversely of the vanes or axially and radially of the rotor. Radial elongation poses no serious problem since the vanes 47 are designed to slide radially during motor operation; however, elongation in the axial direction decreases the clearance provided between the vanes 47 and the end plate surfaces 43, 45. In order to prevent binding between the vanes 47 and the end plates 25, 27 then, it was necessary to provide adequate manufacturing clearance between the vane edges 49, 51 and the end plate surfaces 43, 45 so that when the vane yarns become saturated, sufiicient clearance would still exist therebetween. However, during motor operation at a time when the vane yarns are less than saturated, this clearance was great enough to result in a substantial power loss and a relatively low motor efiiciency.

According to the present invention, this problem has been obviated by a novel vane construction which while providing vane dimensional stability in a longitudinal direction, retains the desirable, strengthening, imbedded woven cloth construction. As seen in FIG. 3, the vane of the present invention includes a mass of molded, plastic material 55 having a woven fiber arrangement 57 embedded therein. The plastic may be any high heat and wear resistant material having low moisture absorption characteristics. A preferred group of materials include the general class of thermosetting plastics of which phe.

nolic thermosetting resins are an example.

The woven fiber arrangement 57 includes warp and weave threads 59, 61 disposed generally perpendicular to each other and interwoven to form a cloth-like construction as shown in FIGS. 2 and 3. According to the present invention, the warp threads 59 are constructed of glass fiber material while the weave threads 61 are formed of an organic or synthetic fiber material such as, for example, linen, cotton, wool or mixtures thereof, nylon, rayon, Orlon or acrylic fibers. The warp glass fiber threads 59 are disposed longitudinally of the vane 47 or in an axial direction relative to the rotor 37 and preferably extend the full vane length, i.e. from the edge 49 to the edge 51. The weave threads 61 are disposed transversely of the vane 47 or in a radial direction relative to the rotor 37 and preferably extend from the edge 53 to the edge 55 of the vane 47.

As described above, the woven cloth 57 embedded in the plastic 55 inherently strengthens the vane 47 in that the. resistance of the vane to shear or fracture under shock loading is increased thereby. In addition to this, the longitudinal or axial glass fiber warp threads 59 have negligible moisture absorption characteristics and undergo virtually no length variation upon exposure thereof to moisture. This is particularly desirable in that it permits heretofore unattainable close manufacturing tolerances between the length of the vane from the edge 49 to the edge 51 and the distance between the end plate surfaces 43, 45. This, in turn, substantially reduces the clearance between the vane edges 49, 51 and the end plate surfaces 43, 45 and significantly increases the efficiency of the pneumatic motor 17.

The weave threads 61 are, as described, preferably constructed of organic or synthetic materials having relatively high absorption characteristics and because of these absorption characteristics these fibers are impregnated by the plastic material 55 during vane formation and provide a strong and reliable vane construction. Of course, these weave threads 61 do absorb moisture and therefore are elongated to a degree during motor use. However, this is not objectionable since the vanes 47 conventionally slide in a radial direction within the rotor slots 39 during rotor rotation so that dimensional change of the vanes 47 in a transverse or radial direction does not affect the motor efficiency.

The glass fiber warp threads 59 are not absorbent and are not impregnated by the plastic material 55 during formation as are the organic fiber weave threads 61. However, the primary stresses on the vane 47 result from shock loading as the vanes rock in an arcuate direction within their slots 39 and are thrown against the outer radial edges of the slots 39. These stresses tend to fracture the vanes 47 along lines longitudinally thereof and the transverse or radially extending weave fibers 61 provide their greatest strength in this direction. Negligible stresses are imposed on the vanes 47 along transverse or radial lines in most installations so the fact that the longitudinal, glass fiber warp threads 59 are not impregnated by the plastic material does not affect the vane life. Furthermore, the glass fiber threads have substantially greater wear resistance characteristics than organic or synthetic fibrous threads so that the vane construction of the present invention increases the vane life.

It will be appreciated that in some high speed rotary tools, the shock and friction loads imposed on the vanes 47 are extremely high so that a considerably stronger vane construction than that required for low speed devices may be necessary. In these devices, the warp threads can be a mixture of glass fiber and organic or synthetic fiber threads arranged in alternate or periodic relation. Thus, the organic or synthetic fiber threads contribute additional strength to the vanes 47 while the glass fiber threads enhance the dimensional stability thereof so that both good strength characteristics as well as high motor efiiciency are achieved.

The vane construction of the present invention is readily formable according to known and conventional manufacturing techniques. Thus, the fiber cloth 57 is woven in a conventional manner by employing existing weaving apparatus. A measure of the selected plastic material 55 such as, for example, a phenolic thermosetting resin is then applied to the cloth 57 so that the glass fiber warp threads 59 are coated and the organic or synthetic fiber weave threads 61 are impregnated thereby. The treated cloth 57 is then passed through calendar-type rolls which apply a relative thick layer of resin 55 thereto to form generally the configuration illustrated in FIG. 3 after which the resin is dried but not set. Thereafter, one, or if desired, several superimposed layers of this material are placed in a hydraulic press and are heated to the setting temperature of the resin so that a homogeneous sheet is formed. If a plurality of superimposed sheets are molded, a construction such as that shown at 63 in FIG. 5 is formed. The sheet can then be cut to size by employing conventional machining techniques to form the vanes 47.

With reference now to FIGS. 4A and 4B, a comparison between the required axial clearance between the rotor vane edge 51 and the end plate surface 45 of the present invention and that of the prior art can be seen. Prior to the present invention, the use of organic or synthetic fiber warp threads running axially or longitudinally of the vane necessitated a clearance between the vane edges 49, 51 and the end plate surfaces 43, 45 which clearance is a function of the length of the vane and the coefficient of expansion of the particular fiber material employed. This clearance is represented at B in FIG. 4B. In the present invention, a clearance represented at A in FIG. 4A is required which substantially is only that necessary to prevent excessive friction between the vanes 47 and the end plates 25, 27. In the prior art, the clearance A was reached only when the vane warp fibers were substantially completely saturated so that normally a clearance somewhere between A and B existed between each edge 49, 51 of the vane 47 and the side plate surfaces 43, 45. This condition resulted in motor power loss and, of course, lower motor efiiciency.

By the foregoing, there has been disclosed an improved, highly efiicient pneumatic motor 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 claims.

I claim:

1. In a pneumatic motor, the combination of a stator having respective end plate means, a rotor journaled within the stator 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 the slot, whereby said vane has a longitudinal edge in sliding engagement with the stator and further has respective side edges, at least one of which side edges has a longitudinal clearance with a respective one of the end plate means, said vane having a reinforcing cloth embedded therein, said cloth comprising interwoven threads including longitudinal and radial threads, only said longitudinal threads including threads being formed of a relatively hard material having relatively low moisture absorbing properties with a consonant relatively low coefiicient of expansion, 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 etficiency.

2. The combination of claim 1, wherein said material comprises glass fiber.

3. The combination of claim 1 wherein said radial threads are constructed of material selected from the group of cotton, wool, linen, rayon, nylon, orlon and acrylic fibers.

4. The combination of claim 1 wherein said vane is constructed of a heat and wear resistant thermosetting plastic.

5. A pneumatic motor vane comprising an elongated fiat member having a generally straight, longitudinal edge and a pair of generally straight, transverse edges, said member having elongated threads embedded in a body of synthetic fabricated material, said threads including threads formed of a relatively hard material having relatively low moisture absorbing properties with a consonant relatively low coefiicient of expansion which extend only in a direction generally parallel to said longitudinal edge, whereby to minimize the coefiicient of friction of said vane longitudinal edge and maximize the longitudinal dimensional stability of said vane.

6. A vane as defined in claim 5 wherein said thread material comprises glass fiber.

7. A vane as defined in claim 5 which includes threads extending in a direction generally parallel to said transverse edges and constructed of material selected from the group of cotton, wool, linen, rayon, nylon, orlon, and acrylic fibers.

3. A vane as defined in claim 5 wherein said synthetic material is a heat and wear resistant thermosetting plastic.

References Cited UNITED STATES PATENTS 2,428,325 9/1947 Collins 161-93 X 2,477,407 7/1949 Grant et al. 161-93 X 2,650,184 8/1953 Biefield 161-93 X 2,818,024 12/1957 Herschel 103-216 X 2,946,315 7/1960 Doeden 91-121 X 2,983,562 5/1961 Runton et al. 308-238 3,131,979 5/1964 Shobert 308-238 3,268,384 8/1966 Frick et al 161-73 3,328,100 6/1967 Spokes et al. 308-238 3,356,292 12/1967 Brewer et al. 91-119 X MARTIN P. SCHWADRON, Primary Examiner.

GEORGE N. BAUM, Assistant Examiner.

US. Cl. X.R.

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