US3618468A - Reciprocating air motor exhaust assembly - Google Patents

Abstract

A RECIPROCATING PISTION AIR MOTOR WITH A PILOT PISTON OPERATED SLIDE VALVE THAT ADMITS AIR ALTERNATELY TO OPPOSITE ENDS OF THE DRIVE CYLINDER OF THE AIR MOTOR THROUGH SEPARATE STRAIGHT AIR PASSAGES WHICH ALSO SERVE AS EXHAUST PASSAGES. THE POSITION OF THE DRIVE PISTION IS SENSED BY STEMS EXTENDING FROM SPOOL VALVES POSITIONED AT OPPOSITE ENDS OF THE DRIVE PISTON CYLINDER CHAMBER. THE SPOOL VALVES CONTROL THE SUPPLY AND EXHAUST TO THE PILOT PISTON, THEREBY CONTROLLING THE SLIDE VALVE AND CONSEQUENTLY PRESSURE TO THE DRIVE PISTON.

Description

Nov. 9, T971 R. K. GARDNER ErAL 3,618,458

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United States Patent O 3,618,468 RECIPROCATING AIR MOTOR EXHAUST ASSEMBLY Richard K. Gardner, Montpelier, and Wilbert G. Kautz,

West Unity, Ohio, assignors to The Aro Corporation,

Bryan, Ohio Filed June 24, 1969, Ser. No. 836,037

Int. Cl. F011 25/06 U.S. Cl. 91-306 2 Claims ABSTRACT OF THE DISCLOSURE A reciprocating piston air motor with a pilot piston operated slide valve that admits air alternately to opposite ends of the drive cylinder of the air motor through separate straight air passages which also serve as exhaust passages. The position of the drive piston is sensed by stems extending from spool valves positioned at opposite ends of the drive piston cylinder chamber. The spool valves control the supply and exhaust to the pilot piston, thereby controlling the slide valve and consequently pressure to the drive piston.

BACKGROUND OF THE INVENTION This invention relates to an improved, reciprocating, fluid driven motor, and in particular to a reciprocating, -uid driven motor that includes a pilot operated slide valve for reversing the direction of the main drive piston of the motor.

Reciprocating type fluid driven motors are common. Also quite common is a reciprocating motor in which a slide valve alternates between two positions to provide for passage of fluid to one end or the other of the drive piston of the motor. In the past, however, there have been some drawbacks in such motors. For example, the power of such motors have been restricted because of icing. Icing occurs when the exhaust lines from the motor become clogged with ice that forms as moisture in the air condenses and freezes due to the rapid expansion of the compressed air during exhaust from the motor. Freezing usually occurs in bends or restrictions in the exhaust lines leading from the air motor and results in blocked air passages. This is just one of the problems that may be encountered with a reciprocating type iiuid motor.

SUMMARY OF THE INVENTION In a principal aspect the present invention of an improved tiuid driven, reciprocating motor provides a cylinder head for the motor which includes the fluid inlet and exhaust passages and cooperates with a control valve through which the uid is directed against one end or the other of the drive piston of the motor. The control valve is pilot operated by means for sensing the position of the piston within the cylinder chamber.

It is thus an object of the present invention to provide an improved, reciprocating piston, uid driven motor.

'It is a further object of the present invention to provide a reciprocating piston diuid driven motor with increased power by providing substantially straight and enlarged inlet and exhaust passages from the opposite ends of the drive cylinder chamber of the motor.

Still another object of the present invention is to provide a reciprocating, uid driven motor which includes means for sensing the position of the drive piston of the motor in order to control reversing of the motor and increasing the speed and eliiciency of the motor.

These and other objects, advantages and features of the invention, will be set forth in greater detail in the description which follows.

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BRIEF DESCRIPTION OF THE DRAWING In the detailed description which follows reference will be made to the drawing comprised of the following iguresz FIG. l is a top plan, partially cut away view of the improved motor of the invention;

FIG. 2 is a cross sectional View of the motor shown in FIG. 3 taken substantially along the line 2-2 in FIG. 3;

FIG. 3 is a schematic cross sectional Iview of the improved motor of the invention with the drive piston approaching the cylinder head end of the motor;

FIG. 4 is another schematic cross sectional view showing the drive piston at the opposite end of the cylinder chamber from that shown in FIG. 3.

FIG. 5 illustrates in graph form comparative data for an old motor, A, and a new motor, B.

DESCRIPTION OF THE PREFERRED EMBODIMENT Attention is initially directed to FIGS. l and 2 which show the construction of a preferred embodiment of the invention. Following this, a description of the mode of operation of the invention is given with reference to FIGS. 3 and 4 for assistance in understanding the cycle of operation of the air motor.

The motor includes a base 10` with a main drive cylinder 12 mounted in a circumferential slot 14 defined in the base 10. A sealing material, for example, a rubber gasket 16 is positioned in the slot 14 between the cylinder 12 and the base 10. Positioned on top of the cylinder 12 is a cylinder head l18 which also includes a circumferential slot 20 with a gasket 22 for receipt and sealing of the cylinder 12. Threaded tie rods as at 23 and nuts as at 25 secure the base 10 and head .18.

A main drive piston 24 is positioned within the cylinder 12 and connected by means of piston washers 26 and 28 and a hub nut 30` to a piston rod 32. Thus, the rod 32 travels in response to the movement of the piston 24. The rod 32 passes through a rod aperture 34 in the base 10. An annular plug 38 is threadably inserted in the base 10 to hold a block 40` in position to bias a spring 42 against sealing washers 44. The washers 44 in combination with an O-ring 46 cooperate to provide a seal about the rod 32 during movement of the rod 32.

Also attached and positioned between the base 10 and head 18 is a straight line tube 48 which is sealed by means of O-ring 501 and 52 in counterbored openings 54 and 56 in the head 18 and base 10 respectively. An inlet or exhaust passage 58, depending upon direction of the piston 2'4 movement is defined in the base 10. The passage 58 leads from the interior of the cylinder 12 through the cylinder port 59 to the tube `48 and is substantially of a uniform diameter. The diameter of passage 58 is substantially equal to the internal diameter of the tube 48. Passage 58 is defined by a center line axis 6.1 which has a substantially constant radius at least equal to the diameter of the passage 58. The passage 58 flares outwardly in a frustoconical shape at the cylinder port 59.

The opposite end of the tube 48 connects with a straight line passage 60 through the head 18 and a valve plate 62. The valve plate 62 is attached to the head 18 by means of screws as at 64 with O-ring seals as at 66 to insure an air-tight seal between the plate 62 and the head 18.

The head 18 and valve plate 62 also include an inlet passage 68 leading to a cylinder port 69 at the end of the cylinder 12 opposite the passage 58. The passages 58 and 68 alternatively act as inlet and exhaust passages to the cylinder 12. An external liuid or air supply passage 70 is also provided for the head 18 leading through the plate 62.

Positioned for slidable movement on the plate 62 is an insert 72. A valve cover 74 is positioned over the insert 72 and a seal is effected therebetween by means of the O- ring 76. This assembly forms the slide valve generally shown at 75. A collar 78 connected to a pilot piston rod 80 is positioned for engagement with the cover 74 to provide coincident movement of the valve cover 74 and insert 72 in response to movement of the rod 80. In the position shown in FIG. 2, the insert 72 does not provide connection of the supply passage 70 with either one of the inlet passages 58 or 68. Movement of the insert 72 to the right would provide a pressure or driving supply of fluid through the passage 68 to the top of the piston 24. Moving the insert to the left would provide a uid supply through passage 58. Exhaust is effected through that passage 68 or passage 58 not connected with the supply passage 70. This arrangement is distinguished from the common iluid motor arrangement wherein the exhaust passages are alternately connected by means of a slide valve to a single exhaust port with the uid inlet then connecting to the passage not exhausting.

The exhaust passage 58 and 68 in each case is substantially a straight line exhaust. Moreover, the diameter of the exhaust passages 58 and 68 is substantially constant and large in respect to prior art constructions. The cross sectional area of the passages is preferably about 1%i0.2% of the cross sectional area of the cylinder chamber. This compares with an average of 0.5% area ratio in older motors.

Although increasing passage size has been known to improve anti-icing characteristics, the combination of large and straight line passages as at 68 and 58 create greater operating efficiency for the reciprocating motor and reduce the possibility of icing Also by ducting the exhaust passages 58 and 68 directly into the atmosphere, greater efciency is realized. The motor may thus run at greater speeds with greater eciency than prior motors of this type as can be seen by referring to FIG. 5.

FIG. 5 illustrates comparative data for an old or prior art motor, A, and a new motor, B, which utilizes the present invention. The dashed lines have as their ordinate the air consumption in cubic feet per minute per horsepower. This is the right hand ordinate in FIG. 5. The solid lines have as their ordinate horsepower. This is the left hand ordinate. The abcissa for the g. is cycles per minute. In each case the motor was `utilized to pump iluid having substantially the same viscosity which for FIG. 5 was less than 1 poise. Also in each case the line pressure to the motors was 120 p.s.i. The data is plotted for a motor having a 31A-inch bore. With the new motor, B, the peak horsepower is almost three times greater and is provided over a much greater range than with the prior art motor, A. Also, the air consumption of the new motor is almost one-half of the prior art motor. Thus, the new motor is almost two times as eilicient.

The control means for effecting movement of the slide valve 75 includes the pilot piston assembly 82 and spool valve assemblies 84 and 86. As shown in FIG. 1 the pilot piston assembly 82 includes a pilot cylinder 88 having therein a pilot piston 90 attached to the rod 80 for reciprocating movement. A bumper 92 is provided at one end of the cylinder 88. The cylinder 88 is held in a housing 94 by means of a cap 96. The pilot piston 90 includes seals 98 between the piston 90 and cylinder 88.

Each spool valve assembly 84 and 86 is constructed in a similar manner. Thus, assembly 84 includes a valve chamber 98 with a cover 100 and gasket 102 over the chamber. A valve insert 104 is positioned in the chamber 98 and is biased against a valve washer 106 and seal 108 by means of a spacer spring 110. A spool element 112 includes O-rings 114 and 116 at its opposite ends. Extending from the end of the spool valve element 112 nearest drive piston 24 through an opening in the head 18 is a rod or stem 118. The rod or stem 118 is positioned to engage the piston 24. The other spool assembly 86 is constructed in a similar fashion and also includes a rod or stem 120 for engaging the piston 24.

As illustrated in FIGS. 3 and 4, fluid or pneumatic passageways are provided to the various sides of the spool valve assemblies 84 and 86 and the pilot piston 90. Thus, air, for example, supplied through the inlet or supply passage passes not only through supply passages 58 and 68 depending upon the position of the slide valve 75, but also passes through a channel 122 in the head 18 to pressurize the upper side of the top spool valve assembly 84. Inlet pressure is also supplied from this point through a channel 124 to the lower end of spool valve assembly 86. The spool valve assembly 84 interconnects one side of pilot piston 90 through a channel 123 with either supply inlet 70 or an exhaust outlet 126. Spool valve assembly 86 connects the opposite side of pilot piston 90 through channel 127 with either supply inlet 70 through channel 122 and 124 or an exhaust outlet 128.

In operation, air entering at the air supply or inlet 70 travels through the slide valve and the tube 48 aS shown in FIG. 3 forcing the piston 24 to the up position. Air above piston 24 exahusts through the port 68. When the piston 24 reaches its extreme up position it engages rod 118 forcing the spool valve 112 into an up position, closing passage from channel 123 to exhaust 126 and allows air to enter from channel 122 through channel 123 to force the pilot piston to the right. Simultaneously, the side valve 75 moves to the right as illustrated in FIG. 4. The opposing air to the right of the pilot piston 90 escapes through the channel 127 and out through the exhaust 128.

After the slide valve 75 has moved, air travels down through inlet port 68. Air below the piston 24 exhausts through the passage 58, tube 48 and passage 60. Air pressure on top of spool valve 112 returns spool valve 112 and rod 118 to original position connecting channel 123 to exhaust 126. When the piston 24 reaches its extreme lower position, it engages the rod causing the spool valve assembly 86 to direct air through channel 127 from channel 124 to the opposite side of pilot piston 90. Air exhausts from the left side of the pilot piston 90 through channel 123 and out exhaust 126.

The stems or rods 118 and .i120 which sense the end of the stroke to operate the slide valve 75 may be variable in length. It has been found advisable to reverse the stroke before the piston 24 bottoms out. The piston 24 then cushions on air rather than bottoming out. Therefore, the action of the motor is smooth and reversal is extremely quick reducing the pressure flow pulse that would normally be present on reversal of a pilot operated motor of this type.

In some instances, however, a measured displacement is desired on the pump end so that the pre-sensing features are eliminated by allowing the piston 24 to strike the sensing valve and bottom out almost simultaneously. For example, with a 3% inch bore motor of the type discussed in relation to FIG. 5, a 1/z-inch stem i118 and 120 provides su'lcient override to prevent bottoming out; whereas, a 1/s-inch stem allows simultaneous reversal and bottoming out and also provides a measured stroke.

What is claimed is:

1. An improved reciprocating fluid driven motor comprising in combination:

a drive cylinder with a cylinder chamber,

a drive piston positioned to reciprocate in said chamber a cylinder head at each end of said cylinder,

a rst straight-line passage from said cylinder chamber through one of said heads to the atmosphere and a second straight-line passage from said cylinder chamber through said other head, including a single bend and terminating as a straight conduit through said one head to the atmosphere substantially parallel to and adjacent said rst straight-line passage.

a uid inlet control valve mounted on said one head, said iluid inlet control valve including a member which alternately connects a fluid inlet with only one of said passages, the other of said passages remaining open as a straight-line passage to the atmosphere, one of each of said passages thereby alternately providing uid for driving said drive piston in said cylinder chamber while the other of said passages exhausts fluid from said cylinder chamber through a straight-line passage having at the most one single bend in said passage, and

means for driving said uid inlet control valve to a1- ternately connect said iluid inlet to one or the other of said passages.

2. The improved .motor of claim 1 wherein said member of said control valve comprises an insert with a uid channel adapted to interconnect said inlet with only one of said passages and also includes a cover over said insert. said including an opening from said channel to said cover such that fiuid pressure biases said cover away from said insert thereby biasing said insert into substantially fluid tight communication with said passages and said inlet.

References Cited UNITEDk STATES PATENTS PAUL E. MASLOUSKY, Primary Examiner U.S. Cl. X.R. 91-313

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