Abstract:
The effects of an air bearing may be augmented in various ways in order to assist in the automated assembly of valve spools into valve bores. Such augmentation may be achieved by agitating one end of the valve spool with sequentially applied pulses of pressurized air as the spool is being lowered into the valve body, increasing the effective length of the valve spool so that the agitation can be applied to the spool when the spool is partially inserted into the body, varying the position of the valve spool while the spool is being inserted into the valve body to expose a length of the spool to the pulses of pressurized air, and applying an oscillating vibration to the fixture that supports the valve body to dislodge a spool that has become jammed in the valve bore.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    The instant application is a divisional of U.S. Ser. No. 11/175,673 filed Jul. 6, 2005, the entire specification of which is expressly incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention relates to a method and apparatus for assembling a valve spool into a valve body. 
       BACKGROUND OF THE INVENTION 
       [0003]    Currently, assembling elongated spools into close fitting valve bodies is a manual operation. The reason for this is that clearance between spool lands and bores is 0.0005 inch, the lands and bores have sharp corners (no lead chamfers), and the bores may not be manufactured to a datum plane. If a bore is machined to a datum plane, then it is a simple matter to orient the bore in a fixture for a later assembly process with the bore oriented in a desired direction, since the orientation of the bore relative to the valve housing is precisely known. If a spool bore is not machined to a datum plane, it is difficult in a later assembly process to precisely align the machined bore with the insertion tooling for a valve spool so that the spool can be inserted into the bore. Even if a bore is machined to a datum plane, a method is still needed to assist the leading end of the spool to find and enter the land bores in the housing. Currently, there is no reliable method or configuration of tooling that will align spools to bores through which a spool can be dropped into a bore with clearance of 0.0005 inches. 
         [0004]    One technique for facilitating the assembly of a spool into a valve bore uses an air bearing as shown in U.S. Pat. No. 5,829,134 for a Spool Valve Loading Method and Apparatus. The method and apparatus described therein uses pressurized gas at a first pressure to advance a valve spool into a valve body bore, and at the same time pressurized gas at a second lower pressure is applied to the valve body bore to create a moving cushion of air that opposes the insertion of the valve spool into the valve bore. The cushion of air from the valve body creates an air bearing that centers the spool in the bore so that the spool can be inserted the full length into the bore without hanging up on the lands of the bore. 
         [0005]    The technique described above provides satisfactory results provided the spool bores are machined to a datum plane. If the spool bores are not machined to a datum plane, since the bores cannot be precisely aligned with the insertion tooling for the valve spools, the spools will jam if the valve body is positioned too close to the insertion tooling. As the gap between the valve body and the insertion tooling is increased, the tooling cannot maintain the alignment of the spool to the bores, with the result that the spools will jam as they are inserted into the bores, or the leading end of the spool will contact and rest on the surface around the entrance to the bore. 
         [0006]    For the foregoing reasons, the air bearing technique, by itself, does not work for all combinations of spool lengths and spool land diameters. Additional assembly aids are needed to produce an assembly system that will successfully load spools over 95% of the time. The features described herein provide the compliance needed for the spool to be inserted into the bore in a valve body in an automated assembly operation. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
         [0007]      FIG. 1  shows various configurations of a valve spool. 
           [0008]      FIG. 2  shows a valve spool that has been inserted into the large bore of a valve body but not into the land bores. 
           [0009]      FIG. 3  shows a valve spool in an off axis position as it begins to enter the small bore of a valve body. 
           [0010]      FIG. 4  shows a valve spool that has been fully inserted into the small bore of a valve body. 
           [0011]      FIG. 5  shows a valve body mounted on a fixture in a raised position and located below a valve spool insertion tool. 
           [0012]      FIG. 6  shows the motion applied to a fixture by a ball oscillator. 
           [0013]      FIG. 7  shows a valve body mounted on a fixture in a raised position with a spool inserted into the large bore of a valve body. 
           [0014]      FIG. 8  shows a valve body mounted on a fixture moving from a raised position to a lowered position with a spool inserted into the top of the small bore of the valve body. 
           [0015]      FIG. 9  shows a valve body mounted on a fixture in a lowered position with a spool inserted into the small bore of a valve body. 
           [0016]      FIG. 10  shows a valve spool with an extension mounted on one end of the spool. 
           [0017]      FIG. 11  shows a valve spool with an extension mounted on one end of the spool being inserted into a valve body. 
       
    
    
     BRIEF SUMMARY OF THE INVENTION 
       [0018]    It has been determined that the effects of an air bearing may be augmented in various ways in order to assist in the automated assembly of valve spools into valve bores. Such augmentation may be achieved by agitating the valve spool as it is being lowered into the valve body, increasing the effective length of the valve spool so that the agitation can be applied to the spool when the spool is partially inserted into the body, agitating the fixture that supports the valve body, and altering the position of the valve spool relative to the agitation source so that the agitation will have a greater effect on the spool. 
         [0019]    A spool is dropped into insertion tooling positioned directly above the valve body. The insertion tooling allows the spool to fall through a nozzle aligned with the bore in the valve body. Near the outlet of the nozzle, small holes are drilled around the circumference of the nozzle. As the spool falls through the nozzle, air is sequentially introduced into the holes. The pulsating air creates an air vortex and causes the top of the spool to move in an irregular pattern. The resulting motion of the spool permits the spool to “oscillate” and eventually find the hole in the small bore of the valve body. The continued application of the air vortex as the spool descends into the valve body tends to push on the spool from the top, oscillating the spool until it clears the nozzle and is fully inserted into the bore. 
         [0020]    To increase the effective length of short spools and expose more area of the spool to the air vortex, a spring or removable extension is mounted on the shaft on the top end of the spool. The combined length of the valve spool plus the extension helps to maintain the perpendicularity of the spool during the drop into the valve bore and provides additional surface area to receive the pulsating air. 
         [0021]    A pneumatic ball oscillator attached to the fixture provides a smooth oscillation motion to the fixture at a sufficient frequency to cause the lower end of the spool that is confined in the bore to move off of any point of rest between the spool and the bore. The ball oscillator provides a smooth, cycloidal type of movement to the fixture. The cycloidal movement of the ball oscillator induces sufficient movement to the valve body and prevents the spool from maintaining one angular position in, or resting within the confinement of, the bore. The oscillator can be set to vibrate differently for each different spool configuration. 
         [0022]    A variable position fixture may also be used to hold the valve body. Depending on spool length and the number of and diameter of spool lands, one position of the fixture may not be sufficient for the air bearing or vortex to move and oscillate the spool. A servo controlled vertical slide allows the position of the valve body to be set for various spool lengths and configurations. After the spool falls into the large bore of the valve body, the bottom end of the spool may come to rest on a surface. Unless the spool end is moved off this surface, it will not drop into the valve bore. If the pulsating air in the nozzle of the insertion tooling is not directly opposite a spool land, the effects of the air vortex on the spool may be minimal. Varying the distance between the valve body and the insertion tooling allows the pulsating air to be directed against the spool at many positions along the spool. As a result, the spool tends go through a series of stop and start movements as it passes the pulsating air in the nozzle. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0023]    Turning now to the drawing figures,  FIG. 1  shows two forms of valve spools  10  and  10   a . Each of the valve spools comprises an elongated shaft  11  and  11   a  on which are positioned a plurality of valve lands  12  and  12   a . The valve lands each have a diameter that is larger than the diameter of the elongated shaft on which they are mounted. The valve lands  12  and  12   a  have various axial lengths depending on the configuration of the valve bodies into which they will be mounted. Such valve spools are well known in the art. 
         [0024]      FIG. 2  shows a valve spool partially inserted into a valve body  15 . The valve body  15  is formed with a large upper bore  16  and a lower smaller bore  18  having a smaller diameter than the diameter of the upper bore  16 . The lower bore  18  forms the valve portion of the valve body, and the lower bore includes a number of lands  19 . The lands on the valve body fit closely around the lands  12  formed on the valve spool. The clearance between the spool lands and the valve lands is typically 0.0005 inches. Such valve spools are typically used in transmission assemblies, but may be used in any device in which spool valves are employed. 
         [0025]      FIG. 3  shows a valve spool that is in a jam position as a result of being angularly misaligned with the axis of the valve bore  18 . The axis  21  of the valve spool  10  is not exactly aligned with the axis of the bore  23  of the valve body  15 . As a result of the misalignment, the lowermost land  12  on the spool is jammed against the upper land  25  formed in the valve body that surrounds the entrance to the small bore  18 . 
         [0026]      FIG. 4  shows a valve spool  10  that is fully inserted into a spool valve body  15 . Although some of the lands  12  on the valve spool are shown as being aligned with lands  27  on the valve body, the alignment of the lands of the valve spool and body is not necessary for the valve spool to be fully inserted into the valve body  15 . What is necessary is that the axis  21  of the valve spool becomes perfectly aligned, for a short period of time with the axis  23  of the bore in the spool valve body. Once the spool enters the bore, the oscillation and gravity cause it to fall to the bottom of the bore as more fully explained below. 
         [0027]      FIG. 5  shows a preferred embodiment of the assembly apparatus in which a fixture  30  is attached to a vertically driven servo slide  31  that is in the up position. The valve body  15  is releasably mounted on the fixture  30 . The servo slide  31  is mounted for controlled motion in a direction that is approximately parallel to the bore axis  23  of the valve body  15 . The motion of the servo slide  31  is only approximately parallel to the bore axis  23  since the bore  18  in the valve body may not have been machined to a datum plane, and as a result, it is impossible to mount the valve body and the fixture on the servo slide so that the bore axis  23  is exactly vertical. In the embodiment that is shown, the servo slide is mounted for vertical motion. The motion of the servo slide  31  is controlled by a servo controller (not shown) and the servo slide is mounted on a slide mechanism such as rails (not shown) as well known in the art. The servo slide  31  may be driven by a mechanism that is electromagnetic, mechanical, pneumatic, or hydraulic in nature, as well known in the art. The servo slide includes an inlet  33  that is coupled to a passageway  34  in the fixture for air that is blown into the valve bore  18  in order to form an air bearing as described in U.S. Pat. No. 5,829,134 described above. With the servo slide in this position, the air bearing air admitted into the valve bore  18  is on. The servo slide  31  allows the valve body  15  to be positioned relative to the insertion tooling  41  described below so that the air bearing has the desired effect. 
         [0028]    A ball oscillator  35  is mounted on the lower portion of the fixture  30 . The ball oscillator provides a smooth cycloidal oscillation motion to the fixture  30  at a sufficient frequency to cause the lower end of the spool  10  that is confined in the bore to move off of any point of rest. Depending on the angular mounting position of the oscillator, the fixture movement can be from 0.000 to 0.002 inch in any direction. Normally, it is from 0.000 to 0.002 inch in any of the three major axis, X, Y and Z. The cycloidal movement of the ball oscillator  35  induces sufficient oscillation in the valve body  15  to prevent the spool  10  from maintaining one angular position and or resting within the confinement of the bores  16  and  18 . The oscillator can be controlled to produce a different oscillation, frequency or amplitude, for each different spool configuration. In the preferred embodiment, the ball oscillator  35  is pneumatic ball rotary device, but other types of oscillators may be used. 
         [0029]      FIG. 6  shows the motion imparted to the fixture  30  and the valve body  15  by the ball oscillator  35 . Accordingly, the fixture and the valve body may be moved 0.000 inch to 0.002 inch in any direction. 
         [0030]    Returning to  FIG. 5 , directly above the valve body  15  is a spool insertion tool  41  mounted on a tooling support  42 . The insertion tool  41  is an elongated hollow body having an axial bore  43  slightly larger that the diameter of the spool lands that will be inserted by the insertion tool. The axial bore  43  has a center axis  45 . The insertion tool  41  is formed with a mounting ring  44  on its outer surface. A mounting plate  46  is attached to the underside of the tooling support  42  by suitable fasteners  47 . The mounting plate  46  is formed with a recess  48  to receive the mounting ring  44  and to secure the insertion tool to the tooling support. The insertion tooling  41  may be attached to the tooling support  42  in ways other than as shown as will be appreciated by those skilled in the art. 
         [0031]    A flared opening  51  is formed on the upper portion of the axial bore  43  of the insertion tool  41  to allow the valve spool to be funneled into the insertion tool without becoming jammed on the top opening of the axial bore. The lower end of the axial bore is formed with a nozzle  53 . A plurality of holes  54  is formed around the circumference of the nozzle  53 . In the preferred embodiment, four holes  54  are equally spaced around the circumference of the nozzle, and are preferably about ⅛ inch in diameter, but other arrangements, numbers and sizes of holes may be used. The holes  54  are formed so that the axis of the holes intersects with the axis  45  of the insertion tooling. The holes may be formed at other angular orientations. Inlet fittings  57  are mounted in each of the holes  54 , and air supply lines  58  are attached one each to the inlet fittings. The air supply lines  58  are coupled to an air controller  59 . The air controller  59  controls the admission of air through the air supply lines  58  to the four holes formed in the nozzle  53  of the insertion tooling. In the preferred embodiment, the air controller  59  causes air to be sequentially introduced into the holes  54 . The pulsating air creates an air vortex in the insertion tooling nozzle  53 , and causes the top of the spool  10  to move in an irregular pattern as the spool falls through the nozzle  53 . The air controller  59  delivers air to air supply lines at a pressures from 15 to 60 pounds per square inch. Although the nozzle is shown formed on the end of the insertion tooling  41 , the nozzle could also be formed as a separate stand alone unit positioned between the insertion tooling and the valve body  15 . 
         [0032]      FIG. 5  additionally shows an escapement slide  64  mounted above the tooling support  42  and a valve spool  10  in the escapement slide. The escapement slide  64  is shown ready to move to the right to drop the spool  10  into the insertion tool  41 . The escapement slide  64  comprises an elongated hollow holder that is dimensioned to receive a valve spool. The position of the escapement slide is controlled by a suitable mechanism that moves the slide back and forth from the position shown where it is adjacent to the opening of the insertion tool  41  to a position shown in phantom which is directly over the insertion tool  41 . When it is directly over the insertion tool, the valve spool  10  will be in alignment with the axis  45  of the insertion tool and the axis  23  of the valve body. 
         [0033]      FIG. 7  shows the valve spool  10  as it is being inserted into the top of the valve body  15 . The servo slide  31  and the fixture  30  are shown in the up position. The air bearing air applied to the inlet  33  is on. The spool  10  has moved to the drop position, and the spool has entered the large bore  16  of the valve body  15 . The vortex air applied to the inlets  57  is turned on during the drop of the spool, and the ball oscillator  35  is turned on. The valve spool  10  is in alignment with the axis  23  of the bore of the valve body. The air controller  59  applies air sequentially to the air inlets  57  so that an air vortex is created in the insertion tooling nozzle  53 . This allows the spool  10  to oscillate laterally as it lowers into the valve body  15 . The pulsating air causes movement of the spool in an irregular pattern and the lower end of the spool will “hunt” until the lowermost land  12  on the spool is exactly aligned with the upper land  19  of the valve body. When the exact alignment occurs, the spool will drop into the lower bore  18  of the valve body. 
         [0034]      FIG. 8  shows the valve spool  10  as the lowermost land  12  on the spool enters the upper land  19  on the valve body. The air bearing air applied to the air inlet  33  is on. The air vortex air applied to the nozzle inlets  57  is on. The servo slide  31  with the fixture  30  is slowly moving down to allow for the maximum effect of the air vortex on the spool  10  as the lowering spool allows the vortex air to impact on both the shaft  11  and the lands  12  of the spool. The rate of descent of the servo slide  31  may be varied until the best results for each different valve and spool configuration are determined by trial and error. The typical rate of descent for the servo slide  31  is one-half inch per second. Depending on spool configuration, this speed may vary. Most spool configurations do not require fixture movement during insertion. One position of the fixture relative to the nozzle is sufficient for most spools to find and drop into their respective bores. The ball oscillator  35  is on to prevent the spool from resting in one place in the valve bore. 
         [0035]    The application of the vortex air to the nozzle  53  of the insertion tool  41  will cause the spool to vibrate slightly as it falls by gravity into the valve body  15 . At the same time, as the spool lowers further into the valve body, the vortex air introduced into the insertion nozzle tends to push on the top of the spool  10  in addition to oscillating the spool until the spool completely clears the insertion nozzle  53  and is lowered into final position in the valve body  15 . 
         [0036]      FIG. 9  shows the servo slide  31  and the fixture  30  in the down position. The air bearing air applied to the inlet  33 , the vortex air applied to the air inlets  57 , and the ball oscillator  35  are all off. The spool  10  is in the fully inserted position in the spool valve housing  15 . 
         [0037]    Automated inspection for the presence of a spool “out of position” may be performed by optical sensors, not shown, positioned at the top of the valve body  15 . If a spool fails to fall below the top surface of the valve body  15 , the sensor will detect this condition and stop the automated assembly process. Such automated inspection processes and the apparatus therefor are well known to those skilled in the art. 
         [0038]      FIG. 10  shows a short length spool  70  with one large land  71  near the top. The shape and mass distribution of spool  70  makes it unstable as it falls into the bore of a valve body. The length of the land  71  is not sufficient to maintain perpendicularity between the spool and the bore  18  as the spool falls into the bore. The bottom end  73  of the spool tends to catch on the surface  25  at the entrance of the small bore  18  as shown in  FIG. 3 , and the spool lies to one side. In this cocked position, the top of a short spool is below the injection tooling nozzle  53 , and as a result, the air vortex in the nozzle has no effect on the spool. 
         [0039]    The effective length of a short spool  70  may be increased by mounting a removable extension such as a spring  72  on the upper end  74  of the spool. The inner diameter of the removable extension  72  is chosen so that it is a slip fit over the outer diameter of end  74  of the spool on which it will be mounted. Once the extension  72  has been mounted on the spool  70 , the spool is loaded into the escapement slide  64  in the usual way. The escapement slide is moved into position over the insertion tooling so that the spool with the extension mounted thereon can drop into the insertion tooling  41 . 
         [0040]      FIG. 11  shows the spool  70  with a spring  72  mounted thereon as the spool enters the lower portion of the valve body. Although the top end  74  of the spool has passed through the nozzle  53 , the upper portion of the spring  72  is still contained within the nozzle. The upper portion of spring  72  presents a surface against which the vortex air can act, and as a result, the vortex air can continue to produce oscillations in the spool  70  after the spool itself has dropped below the insertion tooling nozzle  53 . After assembly of the spool into the valve body  15 , the extension is removed. 
         [0041]    Although the extension has been described as a removable spring, the spring does not have to be removable, and other forms of extension device may be used. For example, if the valve spool when assembled into the valve body includes a spring on the top end of the valve for operational purposes, the spool with the spring attached may be assembled into the valve body as a subassembly. In this situation, the spring is not removed after the spool has been inserted into the valve body. In another example, the extension may comprise a length of tubing that fits over the top end  74  of the spool. The tubing may be formed of metal, nylon or rubber, or other hollow material that may be slip fit over the top end of the spool. 
         [0042]    Although the invention has been described in the environment valve spools used in automatic transmission assemblies, the spool assembly technique described herein can be used for assembling any elongated valve spool into a tight fitting bore. Such constructions may be used on hydraulic valves, pneumatic valves, or other similar configurations in a variety of valve applications. 
         [0043]    Having thus described the invention, various modifications and alterations will occur to those skilled in the art, which modifications and alterations are intended to be within the scope of the invention as defined by the appended claims.