Valve stem polishing method and apparatus

Abstract

 An apparatus and method for polishing combustion engine valves. The machine includes a rotating deburring wheel for on contact with the valve stem and a regulating surface which provides support and applies a rotational force to the valve stem. A pair of guide blades and a guide plate cooperate with the regulating surface to contain the valve stem when contacted by the deburring wheel. The guide blades are positioned at an angle with respect to the axis of rotation of the regulating surface to bias the valve in an inward direction against the guide plate during valve rotation. The machine further includes the use of a unique pivot point for the deburring wheel support so the deburring wheel contacts the valve stem approximately above the valve stem centreline regardless of valve stem diameter or variations in the diameter of the deburring wheel.

Description

[0001] This invention relates generally to the polishing of metallic surfaces, and more particularly, to a method and apparatus for polishing the stem of an internal combustion engine valve.

[0002] Internal combustion engine valves have a tendency to become fouled in use. When such fouling sufficiently reduces the performance, the valves are removed and refurbished. The refurbishment includes removal of carbon deposits by batch cleaning of the valves. Such cleaning process tends to impart minute deformities in the valve surface. The valve surface must be restored to a predetermined finish prior to installing in an engine. One known technique is to grind the valve stems. This involves the removal of material from the valve stem surface which requires that a valve guide insert be positioned in the valve guide to accommodate the reduced valve stem diameter. Such method requires the additional material and labour expense of installing the valve guide inserts.

[0003] A long felt need has existed for a technique for polishing valve stems. In contrast to grinding, polishing is not intended to alter the dimensions of the article. Rather, the surface is restored close to its original finish without a substantial removal of material. A successful technique for polishing valve stems, however, has proved to be elusive. While polishing is not intended to remove surface material, prior attempts at polishing valve stems have either produced an out-of-round condition of the stem or a non-uniform stem diameter.

SUMMARY OF THE INVENTION

[0004] Accordingly, it is an object of the present invention to provide a method and apparatus for polishing valve stems in a manner that does not degrade the surface geometry of the valve. It is further an object to provide a valve stem polishing method and apparatus that is adapted to use by a small repair facility, such as a one-mechanic garage. As such, a method and apparatus according to the invention is fast and easy to use and readily accommodates valve stems of varying diameter.

[0005] According to a first aspect of the invention there is provided an apparatus for polishing the stems of internal combustion engine valves, each valve having a stem and an enlarged head at one end of the stem, the apparatus comprising: a first rotating means in the form of a polishing or deburring wheel for contacting the valve stem surface; a second rotating means, below the first rotating means, for providing a regulating surface supporting and applying a rotational force to a valve stem; and guide blades comprising two strips having spaced apart facing edge portions for receiving the valve stem and cooperating with the regulating surface providing containment for the stem when the first rotating means makes contact with the stem.

[0006] The apparatus may additionally include a guide plate positioned laterally of the rotating means including a circular hole. The guide blades may be positioned at an angle with respect to the axis of rotation of the second rotating means in order to bias a valve extending through the circular hole against the guide plate to provide exceptional stability to the valve being polished.

[0007] Preferably, guide blade adjustment means are provided for adjustably separating the facing end portions of the guide blades, for example at either of two selectable fixed distances. The two selectable spacings will be sufficient to accommodate a wide range of valve diameters. Therefore, ease of use of the apparatus is imparted because the operator need only select one of two positions of an actuator.

[0008] It is preferred for the axis of rotation of the first rotating means to be pivoted about a pivot axis adjacent the deburring wheel such that the deburring wheel contacts the top portion of the valve stem by pivoting the deburring wheel about the pivot axis. The pivot axis is preferably positioned such that the surface portion of the deburring wheel contacts the stem approximately directly above the centre line of the valve stem regardless of either the diameter of the valve stem being polished or variations in diameter of the deburring wheel, which varies according to degree of wear. In a most preferred embodiment of the invention, the deburring wheel has a width that is substantially equal to the length of a typical valve stem so that the valve stem may be polished with a single motion.

[0009] The invention also extends, according to a second aspect of the invention, to a method of polishing a valve stem of an internal combustion engine valve having an enlarged seat at one end of said stem, the method including the steps of: inserting a valve stem into an opening in a guide plate until the valve seat is adjacent the guide plate; supporting the valve stem by a first rotating means having an outer surface adapted to regulate the rotation of the valve stem; providing a pair of guide blades straddling the valve stem positioned therebetween to provide containment in cooperation with the guide plate during polishing; and contacting the top portion of the valve stem with a rotating polishing or deburring wheel to polish the valve stem.

[0010] The invention may be carried into practice in various ways but one form of apparatus and its method of use in the polishing of valve stems will now be described by way of example with reference to the accompanying drawings, in which:

Fig. 1 is a side view of an internal combustion engine valve to which the invention is to be applied;

Fig. 2 is a perspective view taken from the front and right side of an apparatus according to the invention;

Fig. 3 is a sectional side elevation taken along the lines III-III in Fig. 2;

Fig. 4 is a side elevational view taken from the right side of the apparatus in Fig. 2;

Fig. 5 is a top plan view taken along the lines V-V in Fig. 2;

Fig. 6 is a diagram similar to the view in Fig. 3 to illustrate one feature of the operation of the apparatus; and

Fig. 7 is a diagram similar to the view in Fig. 3 to illustrate another such feature.

[0011] Referring now specifically to the drawings, a valve stem polishing apparatus 10 includes a valve support and regulating mechanism 12 mounted to a base 14 and a polishing member 16 pivotally mounted to base 14 above valve support and regulating mechanism 12 (Fig. 2). The purpose of apparatus 10 is to polish the stem of a valve 20 having a circular valve seat 22 and circular valve stem 24 extending from the valve seat (Fig. 1). Because dimensional variations resulting from the removal of surface material from seat 22 may be accommodated by common valve adjustment techniques, there does not exist a need to polish valve seat 22 which may be refurbished by conventional grinding techniques.

[0012] Valve support and regulating mechanism 12 includes a regulating wheel 26 which is rotated counterclockwise, as viewed in Fig. 3, by a motor 28 through a drive mechanism 30. A pair of guide blades 32a, 32b positioned above regulating wheel 26 include facing edge portions 34a, 34b which are spaced apart to define, in combination with an upper surface 36 of wheel 26, a confinement cavity, generally shown at 38 for positioning valve stem 24 during the polishing process. Confinement cavity 38 is laterally bordered on one side by a vertical guide plate 48. Guide plate 48 includes an opening 50 aligned with confinement cavity 38 and having a diameter that is sufficiently large to accommodate any required size valve stem 24 but smaller than the diameter of valve seat 22 (Figs. 2, 4 and 5).

[0013] Positioned above confinement cavity 38 is a rotating polishing wheel 40, which rotates counterclockwise, which is the same direction of rotation as regulating wheel 26. As will be set forth in more detail below, rotation of valve stem 24 is determined substantially entirely by the rotation of regulating wheel 26. Accordingly, valve stem 24 rotates clockwise such that its upper surface is moving in the same linear direction as the surface portion of polishing wheel 40 contacting the valve stem. However, the surface velocity of wheel 40 is greater than that of regulating wheel 26, and hence valve stem 24, such that there is relative movement between the contacting surfaces of polishing wheel 40 and valve stem 24. Polishing wheel 40 is mounted within polishing member 16 which is pivotally mounted by a pivot 42 with respect to base 14. The purpose of this arrangement is to allow an operator to bring polishing wheel 40, which is rotated by a motor 44, into contact with a valve stem 24 positioned within confinement cavity 38. Such pivotal movement of polishing member 16 may be accomplished by applying vertical downward force on a user handle 46 (Fig. 2).

[0014] As best seen in Fig. 5, which is exaggerated for illustration purposes, guide blades 32a, 32b are angularly offset from axis A, about which regulating wheel 26 is rotated, by angle such that facing edge portions 34a, 34b are likewise angularly offset from axis A. In this manner, a valve stem extending through opening 50 and positioned between facing edge portion 34a, 34b will be biased against plate 48, or to the left as viewed in Fig. 5, because the angular orientation of confinement cavity 38 positions the valve stem at a slight angular offset from the regulating wheel 26. The angular offset imparts a lateral force on the valve stem to pull it against the guide plate. This provides lateral stability to the valve stem to prevent "walking". In the illustrated embodiment is one (1) degree.

[0015] Guide blades 32a, 32b may be positioned as shown in the solid lines Fig. 5 and the phantom lines in Fig. 6 in order to polish valve stems of a relatively small diameter, such as 6.35 to 9.525 mm (1/4 to 3/8 inch), or spaced a second distance, as shown in phantom in Fig. 5 and solid lines in Fig. 6 in order to polish valves having a larger stem diameter such as from 9.525 to 12.7 mm (3/8 to 1/2 inch). As best seen by reference to Fig. 6, guide blades 32a, 32b have a thickness T that is preselected to be sufficiently small to allow polishing wheel 40 to engage the surface of a valve stem 24 having a minimum diameter but yet sufficiently thick to retain a valve stem 24′ having a maximum diameter, i.e. a thickness which is more than half the thickness of the maximum stem diameter. In the illustrated embodiment, guide blades 32a, 32b have a nominal thickness T of 3.416 mm (0.1345 inch).

[0016] In order to enhance the ease of operation of polishing apparatus 10, guide blades 32a, 32b are capable of substantially two spacings under the control of a manual actuator 52. Actuator 52 is movable through a 90° arc in order to space the guide blades in one of two positions. Guide blades 32a, 32b are mounted to positioning blocks 54a, 54b which are guided in lateral movement by guide pins 56 (Fig. 3). Movement of positioning blocks 54a, 54b is effected by a shaft 57 having a shaft portion 58a, which is directly connected to actuator 52 and a shaft portion 58b which is coupled to shaft portion 58a by a coupling 60. Shaft portion 58a engages positioning block 54a through a lead thread, for example a 5/8 by 4 triple-lead thread, 62a and shaft 58b engages positioning block 54b through a lead thread 62b having the same dimensions as lead thread 62a except of the opposite hand. In order to provide selective coupling of 58a and 58b, the shafts nest and are not splined. Accordingly, infinite relative adjustment is available. Once alignment is made, coupling 60 is applied in order to retain alignment between the shaft portions. The use of triple lead threads 62a, 62b to couple shaft 57 to positioning blocks 54a, 54b provides sufficient lateral movement of the positioning blocks for a relatively small amount of rotation of shaft 56. This allows the user to select between valves by a mere 90° rotation of actuator 52. In the illustrated embodiment, blocks 54a, 54b are made from a polymeric material.

[0017] In order to prevent a valve from chattering during the polishing process, it is necessary to keep the force vector F applied to the valve stem from polishing wheel 40 either downward or substantially horizontal as shown in Figures 3 and 6. Any upward force vector would tend to create chatter. There are several factors that complicate a successful design. The present use of two discrete positions for guide plates 32a, 32b results in substantial spacing between certain diameter valve stems and the edge portions 34a, 34b of the guide blades. Furthermore, polishing wheel 40 varies in diameter significantly between a new condition and a worn condition. In order to ensure that force vectors imparted by the polishing wheel on the valve stem are horizontal or downwardly pointing, it is necessary to have the most downward point of the polishing wheel contact the most upward point of the stem. Although this could be accomplished by mounting polishing wheel 40 such that it is limited to only vertically reciprocating upward and downward motion, such mounting would require a complicated parallelogram mechanism or the like. Another solution would be to mount polishing wheel 40 for pivotal motion about a pivot point that is an infinite distance from the polishing wheel. This solution is clearly impractical in a compact machine. However, it has been discovered that the objectives of providing only horizontal and downward force vectors on the valve stem from the polishing wheel may be obtained by positioning pivot 42 at the centre of an imaginary circle defined by three points (Fig. 7): the first point 62 is the location of the axis of rotation B of wheel 40 when the wheel is new and in its rest position sufficiently above confinement cavity 38 to provide working clearances; the second point 64 is the location of axis B when the polishing wheel 40 is new and its surface is contacting a valve stem during the polishing operation; and the third point 66 is the location of axis B when polishing wheel 40˝ is worn to its minimum useable diameter and is contacting a valve. By using point 62, 64, 66 to define a circle whose centre is the location of pivot 42, polishing apparatus 10 may still be compact while providing exceptional performance. In the illustrated embodiment, point 42 is located such that the point of valve stem 24 contacted by polishing wheel 40 does not vary by more than +/- 1/2 of a degree regardless of the working diameter of the polishing wheel or the diameter of the valve stem. This may be accomplished by positioning pivot 42 at a radius of 106.2 mm (4.18 inch) from axis B, 106.7 mm (4.20 inches) behind the centreline separating facing edge portions 34a, 34b and (46.5 mm) 1.83 inches above the centreline of a hypothetical 6.35 mm (1/4 inch) diameter valve stem being polished.

[0018] In the illustrated embodiment, regulating wheel 26 is 60.325 mm (2-3/8 inches) in diameter and is made from a nitrile having a durometer of 65 +/- 5 shore A and is rotated at 70 rpm. Polishing wheel 40 is a grade 7A-fine deburring wheel manufactured by 3M Company under Model Scotch Brite SST, having a new diameter of 152.4 mm (6 inches) and a width of 152.4 mm (6 inches). Polishing wheel 40, in the illustrated embodiment, may be used until it is worn to a diameter of 101.6 mm (4 inches). Polishing wheel 40 is rotated at 1725 rpm by a 250 watts (1/3 horsepower) motor. The above provides relative surface speeds between the regulating wheel and the polishing wheel and appropriate coefficients of friction to ensure that the regulating wheel will have greater frictional engagement with the valve stem than the polishing wheel, while maintaining the speed of the regulating wheel to a level that allows easy loading and unloading of a valve stem.

[0019] In use, actuator 52 is placed in the appropriate position for the valve stem diameter to be polished. Each position accommodates a range of valve stem diameters. The valve is then inserted stem first through opening 50, which will place the valve stem in confinement cavity 38 in contact with upper surface 36 of regulating wheel 26. Regulating wheel 26 will rotate the valve stem and place a lateral force on the valve stem, resulting from the angular displacement of guide blades 32a, 32b, which will pull the valve untilits seat is against vertical guide plate 48. With the valve stem fully loaded into the apparatus, the operator applies a downward force on handle 46 to bring polishing wheel 40 into contact with the valve stem. Polishing wheel 40 is sufficiently wide to polish most valve stems in one pass.

[0020] It has been discovered that individual users have a tendency to place significantly different downward forces on handle 46. If too much downward force is exerted, then motor 44 may eventually shut down temporarily due to a thermal overload. In order to avoid this, a meter 68 is provided in order to monitor the amperage, and hence the load, of motor 44. This encourages uniform application of polishing force by the operator. After a while, use of apparatus 10 results in an uneven surface to polish wheel 40. A dressing cylinder (not shown) may be inserted between opening 70 and an opposing saddle 72 in the housing of valve support and regulating mechanism 12. Such a dressing wheel will typically have an outer surface of silcon carbide. Once the dressing wheel is positioned between opening 70 and saddle 72, the user pulls down on handle 46 in a same manner as polishing a valve. However, the surface of wheel 40 will contact the dressing cylinder which will remove material from polishing wheel 40 to a uniform diameter across its width.

[0021] This method and apparatus described do not remove a substantial amount of material from the valve stem, leaving the valve stem substantially at its original diameter. This allows the refurbishing of an internal combustion engine valve without the necessity of a valve guide insert in order to accommodate a changed valve diameter. Valves may be polished by applying a single downward force by the operator and no more than a 90° turn of a selecting actuator to accommodate various valve stem diameters. This is accomplished without inducing chatter in the rotating valve notwithstanding the accommodation of various valve diameters and notwithstanding variations in the diameter of the polishing wheel. Because the valve stem is rotated without chucking or other such limiting means, an exceptionally uniform polishing effect is applied across the entire surface of the valve stem without a tendency to make the valve stem out-of-round. The invention may be embodied in a portable machine that is relatively inexpensive, and hence, suitable for use by a small repair facility.

Claims

1. An apparatus (10) for polishing the stems of internal combustion engine valves, each valve (20) having a stem (24) and an enlarged head (22) at one end of the stem, the apparatus comprising: a first rotating means in the form of a polishing or deburring wheel (40) for contacting the valve stem surface; a second rotating means (26), below the first rotating means, for providing a regulating surface supporting and applying a rotational force to a valve stem; and guide blades (32a,32b) comprising two strips having spaced apart facing edge portions (34a,34b) for receiving the valve stem and cooperating with the regulating surface providing containment for the stem (24) when the first rotating means (40) makes contact with the stem.

2. An apparatus according to claim 1 in which the first and second rotating means (40,26) rotate in the same direction.

3. An apparatus according to claim 1 or claim 2 in which the first rotating means (40) is pivoted about a pivot (42) that is selected to provide placement of the polishing or deburring wheel (40) at a point directly over the centreline of the valve stem (24) regardless of valve stem diameter or polishing or deburring wheel operating diameter.

4. An apparatus according to claim 1 or claim 1 or claim 3 in which the relative speeds and the coefficients of friction of the said first and second rotating means (40,26) are such as to prevent the movement of the valve stem.

5. An apparatus according to any of claims 1 to 4 in which the guide blades (32a,32b) are each positioned at an angle relative (X) to the axis of rotation of said second rotating means to provide a force along the longitudinal axis of the valve stem (24) to hold the valve stem during rotation.

6. An apparatus according to claim 5 in which the said angle is one degree.

7. An apparatus according to any of claims 1 to 6 which includes a load meter (68) for determining the load on said first rotating means (40).

8. An apparatus according to any of claims 1 to 7 in which the polishing and deburring wheel (40) has a width substantially the same as the length of a valve stem (24).

9. An apparatus according to any of claims 1 to 8 which includes a guide plate (48) lateral of said wheels and including a circular hole (50) for accepting a valve stem.

10. An apparatus according to any of claims 1 to 9 which includes guide blade adjustment means (52,54a,54b,56,57) providing adjustable separation of said facing edge portions (34a,34b) at either of two selectable fixed distances.

11. An apparatus according to claim 10 in which said blade adjustment means includes a manual actuator (52) which adjusts the separation of said guide blade edge portions (34a,34b) to either of said fixed distances through 90° of rotation of said actuator.

12. An apparatus according to claim 10 or claim 11 in which said adjustment means includes left and right hand triple pitch lead threads (62a,62b) which are joined with a collar (60).

13. A method of polishing a valve stem (24) of an internal combustion engine valve (20) having an enlarged seat (22) at one end of said stem, the method including the steps of: inserting a valve stem (24) into an opening (50) in a guide plate (48) until the valve seat (22) is adjacent the guide plate; supporting the valve stem by a first rotating means (26) having an outer surface adapted to regulate the rotation of the valve stem; providing a pair of guide blades (32a,32b) straddling the valve stem positioned therebetween to provide containment in cooperation with the guide plate (48) during polishing; and contacting the top portion of the valve stem with a rotating polishing or deburring wheel to polish the valve stem.

14. A method according to claim 13 which includes pivoting the axis of rotation of the rotating deburring or polishing wheel (40) about a pivot axis (42) adjacent the wheel to bring the wheel into contact with the valve stem.

15. A method according to claim 14 which includes positioning the pivot axis (42) such that the surface portion of the wheel (40), contacting said stem, is directly above the centreline of the valve stem regardless of valve stem diameter.

16. A method according to claim 13 or claim 14 or claim 15 which includes monitoring the load applied to the wheel (40) during said contacting in order to apply the proper force of the wheel to the valve stem.

17. A method according to any of claims 13 to 16 which includes placing the guide blades (32a,32b) at an angle, preferably of one degree, relative to the axis of rotation of the first rotating means (26) so that a force is produced tending to hold the seat of a valve against the guide plate (48).

18. The method of polishing the stems of internal combustion engine valves each valve having a stem (24) and an enlarged head (22), the method comprising the steps of: providing a first rotating means including a polishing or deburring wheel (40) and means to engage said valve stem surface with said wheel; applying a rotational force to said stem with a second rotating means (26) located below said first rotating means and having a regulating surface to support said valve stem; and containing said valve stem when said first rotating means makes contact with said stem using two strips (32a,32b) having spaced apart facing edge portions (34a,34b) which receive said stem therebetween.

19. A method according to claim 18 which includes rotating said first and second rotating means in the same direction and preferably at relative speeds such that the coefficient of friction of the second rotating means will control rotation of the valve stem.

20. A method according to claim 18 or claim 19 in which said first rotating means (40) is positioned on a pivot arm to provide contact of said wheel at a point directly over said valve stem centreline regardless of valve stem diameter.

21. A method according to claim 18 or claim 19 or claim 20 in which said guide blades are positioned at an angle, preferably one degree, relative to the axis of rotation to provide a force holding said valve stem inward during rotation of said second rotating means.

Drawing