US3525580A - Wear and tear-compensating high-pressure gear pump - Google Patents

Description

O. ECKERLE Aug. 25, 1970 WEAR AND TEAR-COMPENSATING HIGH-PRESSURE GEAR PUMP Filed Aug. 29, 1968 7 Sheets-$heet '2 INVENTOR Ct to Eck e rl e ATTORNEY.

5, 1970 o. ECKERLE 3,525,580

WEAR AND TEAR-COMPENSATING HIGH-PRESSURE GEAR PUMP Filed Aug. 29, 1968 7 Sheets-Sheet 3 Zia-i.

INVENTOR Otto Eckerle I ATTORNEY 1970 0. ECKERLE. 3,525,580

WEAR AND TEAR-COMPENSATING HIGHPRESSURE GEAR PUMP Filed Aug. 29, 1968 7 Sheets-Sheet 4 fi -i LZLSLQ 3 6466655866575610 '1 x 4 A A H /M Z/I* 77 INVENTOR Otto Eckerle ATTORNEY O. ECKERLE Aug. 25, 1970 ESSURE GEAR PUM? WEAR AND TEAR-COMPENSATING HIGH-PR Filed Aug. 29, 1968 7 Sheets-Sheet 5 ,mvsmrm 0H0 Eckerle BY w ATTORNEY 0. ECKERLE Aug. 25, 1970 WEAR AND TEAR-COMPENSATING HIGH-PRESSURE GEAR PUMP Filed Aug. 29, 1968 7 Sheets-Sheet 6 fag INVENTOR 0H0 Eckerle ATTORNEY o. ECKERLE Aug. 25, 1970 WEAR AND TEAR-COMPENSATING HIGH-PRESSURE GEAR PUMP 7 Sheets-Sheet 7 Filed Aug. 29, 1968 INVEN TOR 0H0 Eckerle ATTORNEY United States Patent US. Cl. 418-126 17 Claims ABSTRACT OF THE DISCLOSURE Wear and tear-compensating high-pressure gear pump comprising a driven externally-geared pinion, a concomitantly rotating intemally-geared wheel, a movable sickle-shaped filler member between the pinion and the internal gear and either one or two axial disks covering the gears laterally, as well as an insert member, called control piston, being disposed on the pressure side of the gears and being radially displaceably arranged with respect thereto, enclosing the outer circumferential surface of the internal gear in a specific angular range and touching the latter as the sole stator part, said control piston containing the first portion of the pressure outlet duct, being relieved for the major part with regard to radial forces and hence pressing against the circumference of the internal gear with only a limited amount of excess force so that as a result the internal gear is essentially supported only on the pinion, on the one hand, and on the filler member, on the other hand, characterized in that the pump housing (1) is eccentrically bored with respect to the pinion shaft (3) in such a manner that the center (M of the housing bore (7) is positioned on the hydraulic line of application or effective curve (W which extends of necessity also through the internal gear center (M and in that the control piston is accommodated in the sickle-shaped space being formed due to the eccentricity between the internal gear (4) and the housing bore (7 being essentially adapted to the configuration thereof.

BACKGROUND OF THE INVENTION Field of the invention The present invention relates to a wear and tearcompensating high-pressure gear pump comprising a driven externally-geared pinion, a concomitantly rotating internally-geared wheel and a movable sickle-shaped filler member between the pinion and the internal gear, as well as an insert member, called control piston, which is disposed on the pressure side .of the gears and radially displaceably arranged with respect thereto, and which encloses or surrounds the outer circumferential area of the internal gear in a specific angular range, touching the latter as the sole stator part. This insert member contains the first portion of the pressure outlet duct, is relieved for the major part with regard to radial forces and hence presses against the circumference of the internal gear with a limited excess force so that the internal gear is supported essentially only on the pinion, on the one hand, and on the filler member, on the other.

Description of the prior art In the known pumps of this type, the control piston is positioned in one recess each of the pump housing and of a cover being specifically provided for the control piston. By virtue of this arrangement, the angle at which the control piston encloses the outer circumferential surface of the internal gear is only small. Furthermore, the control piston has a complicated construction since it must not only be radially movable with respect to the Ice internal gear, but also has to compensate for inclined or slanted positions of the internal gear which are due to wear and tear.

SUMMARY OF THE INVENTION In order to eliminate the disadvantages and drawbacks of the known pumps as outlined above, the present invention proposes that the pump housing be eccentrically bored with respect to the pinion shaft in such a manner that the center of the housing bore is positioned on the hydraulic line of application, or effective curve, which extends of necessity also through the internal gear center, and so that the control piston is accommodated within the sickle-shaped space formed due to the eccentricity between the internal gear and the housing bore and is adapted to the configuration of that space.

Since the control piston is thus positioned within the housing bore, the recesses in the housing and in the cover, which serve for guiding it, as well as the otherwise required seals or gaskets are rendered unnecessary. The control piston can enclose the internal gear within an angular range of up to and above, which results in a stabler positioning, that is less sensitive to vibrations, of the internal gear on the control piston. In addition thereto, the control piston may be manufactured in a simple manner inasmuch as its surface is composed of plane and circular surfaces.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view of an embodiment of the invention.

FIG. 2 is a cross-sectional view taken along lines IIII of FIG. 1.

FIG. 3 is a cross-sectional view of another embodiment of the suspension means of the control piston 10 of FIG. 1.

FIG. 4 shows a detail of the radial pressure field 22 of FIG. 1.

FIG. 5 is a cross sectional view taken along VV of FIG. 4.

FIG. 6 is a cross sectional view, with portions cut off, of another embodiment of the control piston 10 of FIG. 1.

FIG. 7 is a view along the arrow 7 of FIG. 6.

FIG. 8 is a cross sectional view of the pump of the invention dealing primarily with means to eliminate the differences in pressure and excessive wear and tear upon the filler member of the control piston 10 and the internal pressure and is shown in cross section VIIIVIII of FIG. 9.

FIG. 9 is a cross sectional view with portions eliminated, taken on line IXIX of FIG. 8.

FIG. 10 is a cross sectional view of a portion of the pump of the invention showing an additional improvements of the support of the control piston.

FIG. 11 is a cross sectional view of the pump of the invention showing still additional means of suspending the control piston 10.

FIG. 12 is a cross sectional view taken along line XIIXII of FIG. 11.

FIG. 13 is a cross sectional view also taken along line XIIX II of FIG. 11, showing a different manner of positioning the axial disk 73.

FIG. 14 is a schematic diagram showing another means of suspension of the control piston 10.

FIG. 15 is a modification of the embodiment of FIG. 11.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Various embodiments of the present invention are illustrated in the accompanying drawings wherein like elements are identified with the same reference numerals.

al view and in .FIG. 2 in a view taken along line II-II of FIG. 1 consists of the housing 1, the pinion 2 with the driven pinion shaft 3, the concomitantly rotating internally-geared wheel 4 and the sickle-shaped filler member 5 which is movably positioned on the bolt 6. The housing bore 7 is eccentrically hollowed out with regard to the center M of the pinion shaft 3 in such a manner that the hydraulic line of application or effective curve W which extends axially through the suction connection 8 and the pressure connection 9 also extends through the center M of the housing bore 7 and the center M of the internal gear 4.

Mounted on the pressure side of the pump between the internal gear 4 and the housing bore 7 is a control piston 10 which is secured in its position against rotation by means of a pin 11. As illustrated in FIG. 2, the pin 11 engages on both sides with one square head 12 each in a flat milled-out portion 13 of the housing parts 14. Accordingly, the control piston 10 is supported on the housing part 14 respectively by way of a spacer tube 15 and a retainer ring 16. The pin 11 has in its center a small collar or flange 17 which, due to the short guide thereof in the bore of the control piston 10, allows for a limited alignment of the control piston 10 toward the gear elements 2 and 4.

In order to achieve a compensation of the radial forces, three pressure pistons or rams, for example ring pistons 18 made from plastic material, are provided within the control piston 10 and their end faces are rounded off or chamfered in such a manner that they have only a limited area of contact with the housing bore 7. The space below each ring piston is'in operative connection with the pressure space of the pump by way of a bore 19 which terminates in a recess 20 of the control piston 10. A further bore 21 extends from the recess 20 to the space 22 between the control piston 10 and the housing bore 7 which is delimited by the ring piston 18. The ring pistons are further provided with sealing rings 23 and are subjected to the action of cup or undulated springs 24. By virtue of this construction, the ring pistons 18 are pressed against the housing bore 7by means of the undulated springs when the pump begins to run, and by means of the pressure medium during the operation of the pump with only a small amount of force, and only low frictional forces will be produced when the control piston 10 becomes displaced due to wear and tear of the internal gear.4. Pressure fields are formed or built up in the spaces 22 between the ring pistons 18 and the housing bore 7 which press the control piston 10 against the internal gear 4 and the latter against the filler member 5 and the pinion 2, so that the pinion 2 will comb or mate with the internal gear 4 Without backlash of the toothed wheels. The relieving pressure field which is being built up within the recess 20 and which is delimited by means of transverse grooves 25 and 26 in the control piston 10, that are under the effect of suction pressure, counteracts the pressure fields mentioned above. The control piston 10 encloses the internal gear 4 within an angular range of slightly more than 180. In order not to impair the possibility of a radial displacement of the control piston 10,- the latter is provided at the ends of the outer circumference with milled-out surfaces 27 and/ or 28. In order to assure that the conveying medium can flow from the suction side to the pressure side, the internal gear 4 has radial bores (not shown) extending between each tooth gap and the circumferential surface of the internal gear 4.

FIG. 3 illustrates another embodiment relative to the suspension of the control piston 10. The central pressure piston 29 is guided Within a bore of the housing 1 and has at its inner end a spherical surface 30 which engages in a spherical indentation 31 of the control piston 10, thus securing the latter against rotation. This measure affords the advantage that the control piston 10 can become adjusted or aligned with regard to the gearing almost free 4- from any forces, while nevertheless being secured against rotation.

A particular embodiment of the circular radial pressure field (22 in FIG. 1) is illustrated in FIG. 4 as well as in FIG. 5, the latter being a cross-sectional view taken along line VV of FIG. 4. A pocket bore 33 is so disposed in the annullar bore or recess 32 of the control piston 10 that a groove 34 is produced. A sheet metal ring 36 having a beaded edge 35 is guided within the bore or recess 32 with a small gap S whose beaded edge abuts or rests against the housing bore 7. The sheet metal ring 36 which engages with a nose or projection 37 in the groove 34, thus being secured against rotation, has the advantage that it cannot become canted by reason of its small thickness. The gap S is sealed by means of an O-shaped ring 38-which is pressed against the sheet metal ring 36 by a cup and, respectively, an undulated spring 24 by way of a plastic ring 39. The plastic ring 39 is likewise fixed in position within the groove 34 by way of a nose or projection 40. As an aid during assembly serves a tubular rivet 41 whose flange 42 prevents the sheet metal ring 36 from falling out.

Another embodiment of the control piston 10 is illustrated in a cross section in FIG. 6, and in FIG. 7 viewed in the direction of the arrow VII. The pressure piston 43 which is made according to the injection molding process for plastics comprises a stud 45 having slots 44 and a collar portion 46 at the lower end thereof. During the introduction of the stud 45 into the bore 47 of the control piston 10, the collar 46 locks behind a projection 48 in the bore 47. The pressure piston 43 is secured in position by means of a cam 49 being provided at the stud 45 and engaging in a groove 50 of the control piston 10. A nose 51 serves as an aid for the introduction of the stud 45. The outer edge of the pressure piston 43 is provided with a rounded-off portion 52 so as to prevent canting. The surface 53 of the pressure piston 43 is supplied with pressure medium by way of the bores 54, thus being hydrostatically relieved. This relief is necessary for the following reason: During the deflection of the pinion shaft 3 and as a result of abrasion, the control piston 10 executes a slight rotary movement about its point of suspension near the tooth engagement. During this rotary movement, the pressure fields at the outside diameter of the control piston 10 must execute a slight displacing movement at the inside diameter of the housing. In order not to obstruct this displacing movement, a hydrostatic relief of the pressure fields toward the inside diameter of the housing is necessary. The central pressure piston 43' is constructed in an analogous manner, but it has an axial opening 55 which serves for the discharge of the medium that has been conveyed.

The pump shown in FIG. 8 in a cross section taken along the line IXIX of FIG. 9, and in FIG. 9 in a cross section taken along line VIII-VIII comprises means for partially relieving the rfiller member. It has been found that the filler member is subjected to a greater degree of wear and tear since the pressure of the control piston 10 which is exerted on the filler member by way of the internal gear '4 is greater than the internal pressure. This disadvantage is obviated by the measures which will be described hereinafter.

The control piston 10 is wider than the internal gear 4 and is supported on the axial disk 58 by means of a collar 57 formed by a perforation or aperture 56. The axial disk 58 is disposed rotatably about the pin 59 and comes to abut or bear against the pinion shaft 3 with a cylindrical bore or recess 60. The control piston 10, on the other hand, is supported only against the surface element 61 of the axial disk '58. Within the area of the tooth engagement, the control piston 10 is not supported on the axial disk 58 so that at that point it will push the internal gear 4 into the flanks of the piston 2. It is possible to keep the filler member slightly larger in its outside diameter so that the control piston 10 will initially not come to abut against 61, but will do so only after the filler member has been introduced. Due to the spring action of the collar 57, existing tolerances may be bridged. The bolt 62 serving for the suspension of the filler member is chamfered at the ends on both sides and guided displaceably within a slot 63 of the axial disk 58.

The axial disk 58 comprises a recess 64, building up a pressure field, and a piston 56 which is sealed with the aid of a loop ring 66 is guided in the recess 64. The supply of the pressure field is effected by way of the bore 67. The piston 65 is provided annular so that only a limited friction arises between the piston and the axial housing part 68. During the deflection of the pinion shaft 3, the axial disk 58, by virtue of its almost floating position, can be additionally slid on to the pinion shaft 3 by the control piston 10. The contact surface of the axial disk 58 with the pinion shaft 3 may be lubricated with pressure oil through the bore 69.

In the above-described construction of the pump, the surface pressure between the internal gear and the filler member is reduced since the control piston is supported not only upon the internal gear but, by way of the axial disks, also upon the pin thereof and the pinion shaft 3 so that the contact pressure is distributed to a greater area and the total wear and tear is reduced. Also taken into account is the problem that, in a newly installed pump, the internal gear does not simultaneously abut against the filler member with the control piston at the axial disks. If the tiller member, when new, is provided with a larger outside diameter, the control piston 10 does not press upon the axial disk while the sealing of the pressure space is nevertheless assured. When the pump is placed in operation, an increased abrasion at the filler member (running-in abrasion) will therefore take place until the control piston with the collar thereof will abut against or bear on the axial disk.

FIG. 10 shows a further possibility for supporting the control piston 10 by way of the axial disk 58 on the pinion shaft 3 and the pin 59. The surface element 61 of the axial disk 58 is elastically provided by means of a bore 70 and a slot 71 so that, due to the resilience of the element 72, a compensation of the differences in the abutment of the internal gear against the filler member, or its contact therewith, and of the control piston 10 at and, respectively, with the axial disk 58 can take place.

A still further possibility of suspending the control piston 10 is illustrated in FIGS. 11 to 14. The axial disk 73 is positioned on the pinion shaft 3 and provided with a bore into which engages a pin 74 which, in turn, is positioned in the control piston 10. When a force is exerted toward the center of the housing by the pressure fields 75, the control piston 10 will press the internal gear 4 in a tooth engagement upon the flanks of the pinion 2 while simultaneously turning or rotating the axial disk 73 about the center 76 of the pinion shaft 3, until the internal gear 4 comes to rest against or bear against the filler member 5. This solution avoids the disadvantage which arose as a result of the heretofore known measures, and specifically that, during the abrasion of the filler member 5 and due to the change in the position of the internal gear center 77, a displacement of the gearing took place while, however, the control edges in the axial disk and in the control piston as well as the position of the pressure fields were maintained.

The schematic showing of FIG. 14 indicates these interrelations. When the filler member is worn, the internal gear 4 with its pitch circle or circle of contact 79 and/or 79 rolls along on the pitch circle 78 of the pinion. The center 77 of the internal gear 2 executes at that time a rotary movement about the center 76 of the pinion shaft and travels toward point 77'. The pitch point, or instantaneous center of motion, 80 is shifted to 80'. By means of the axial disk 73 being rotatably suspended in point 76, the in 74 and/or 74' is moved, pulling behind the control piston, so that also the resultant 81 of the pressure fields is pulled behind about the angle on to 81'; in other words, the wear and tear of the filler member and the automatic re-setting of the internal gear have changed nothing with regard to the existing control and force conditions.

FIG. 12 is a cross-sectional view taken along line XI[--XII of FIG. 11. The axial disk 73 is axially relieved with regard to the cover 83 by means of a pressure field 82 so that the re-setting of the axial disk 73, the internal gear 4 and the control piston 10 will not be met with or opposed by a high frictional resistance. The pressure piston 84 consists of an endless wire having a rectangular crosssection which is formed according to the recess 64 in FIG. 8 and sealed off by means of an O-shaped ring 85. The control piston 10 is secured in position with respect to the axial disk 73 by way of the pin 74 which, in the center of the control piston, can be readily adjusted to the gearing. The pin 74 projects with its extension 87 into a bore 88 of the cover 83. The collar 89 has play in the bore 88 so that the control piston 10 can execute together with the axial disk 73 a rotary movement about the pinion shaft 3 (see FIG. 14) until the collar 89 rests against or makes contact with the bore 88. The play of the collar 89 in the bore 88 is so designed that, following the abutment or hearing of the collar 89 in the bore 88, the filler member has run in and corresponds in its contour precisely to the crown lines or circles of the gears. In case of a pressure increase, both the pinion shaft 3 and also the filler member bolt 6 will deflect. In order to also compensate for the gap being formed during this deflection, the bolt is provided elastic. This may be accomplished, for example, in that the pin is weakened in its moment of resistance in the area of the extension 87 by a reduction of the crosssectional area.

FIG. 13 is equally a cross-sectional view taken along line XII-XII of FIG. 11. The difference as compared to FIG. 12 consists in the manner of positioning the axial disk 73: In this embodiment, the positioning is effected on a bearing bushing 90. The positioning of the axial disk 73 could, of course, also be made on a corresponding cylindrical shoulder portion of the cover 83.

FIG. 15 illustrates a modified embodiment of the pump shown in FIG. 11, wherein the control piston 10 has been indicated only schematically. This embodiment is based upon the following deliberation: As a result of the different operating conditions to which these pumps are subjected, for example pressure, rate of revolutions, temperature, viscosity, the hydraulic load on the filler memmber 5 varies, i.e. in the embodiments in which the control piston 10 is supported by way of the axial disks it is possible that the filler member is pressed to an increased extent against the crown circle diameter. This fact causes a wear and tear which can no longer be com pensated by the compensating pressure fields of the control piston because of the support of the control piston on the pinion shaft 3 via the axial disks. In order to obviate this disadvantage, it is necessary that the filler member and the axial disk be so suspended that minor moments acting upon the filler member, the housing, the control piston and the pinion shaft are transferred without loading or charging the gliding surfaces of the filler member.

For this purpose, the axial disks 91 are rotatably positioned on the pinion shaft 3 and connected with the filler member 5 by means of a cylindrical pin 92, and the aggregate which is thus formed is supported against a housing pin 93 being secured to the housing. The filler member 5 is provided at the thicker end thereof with a surface 94 and bears therewith against a surface 95 of the housing pin 93 which is rotatably and/ or displaceably positioned in bores of the axial housing parts so as to be adapted to execute the gliding movements that are required due to the deflection of the pinion shaft.

It should be understood of course that the foregoing disclosure relates to only preferred embodiments of the invention and that it is intended to cover all changes and modifications of the examples of the invention herein chosen for the purposes of the disclosure which do not constitute departures from the spirit and scope of the invention set forth in the appended claims.

What is claimed is:

1. Wear and tear-compensating high-pressure gear pump comprising a driven externally-geared pinion, a concomitantly rotating internally-geared wheel, a movable sickle-shaped filler member between the pinion and the internal gear and at least one axial disk covering the gears laterally, as well as an insert member, called control piston, being disposed on the pressure side of the gears and being radially displaceably arranged with respect thereto, enclosing the outer circumferential surface of the internal gear in a specific angular range and touching the latter as the sole stator part, said control piston containing the first portion of the pressure outlet duct, being relieved for the major part with regard to radial forces and hence pressing against the circumference of the internal gear with only a limited amount of excess force so that as a result the internal gear is essentially supported only on the pinion, on the one hand, and on the filler member, on the other hand,

characterized in that the pump housing 1 is eccentrically bored with respect to the pinion shaft 3 in such a manner that the center M of the housing bore 7 is positioned on the hydraulic line of application or effective curve W which extends of necessity also through the internal gear center M and in that the control piston 10 is accommodated in the sickleshaped space being formed due to the eccentricity between the internal gear 4 and the housing bore 7, being essentially adapted to the configuration thereof.

2. High-pressure gear pump according to claim 1,

characterized in that the control piston 10 encloses the internal gear 4 within an angular range of approximately 180. 3. High-pressure gear pump according to claim 1 characterized in that hydrostatically relieved circular pressure fields 22 are provided in the outer circumferential surface of the control piston 10, said pressure fields being formed by pistons positioned in the control piston and being in operative connection with the pressure space of the pump via bores 21. 4. High-pressure gear pump according to claim 3, characterized in that the edges of the pistons are chamfered, in that the rear of the pistons is charged by means of a charging spring and are in operative connection with the pressure space of the pump via a bore 19.

5. High-pressure gear pump according to claim 1,

characterized in that the central pressure and, respectively, ring piston 29 is guided within the housing 1 and is provided at the inner end thereof with a spherical surface 30 engaging in a spherical indentation 31 of the control piston 10.

6. High-pressure gear pump according to claim 1,

characterized in that the ring pistons 18 are replaced.

by sheet metal rings 36 having a beaded edge 35 and being supported via an O-shaped ring 38 and a plastic ring 39 each on a charging spring, said sheet metal ring 36 and said plastic ring 39 engaging each with one nose in a groove 34 of the annular recess or bore 32, said sheet metal ring having a gap S with respect to the recess or bore.

7. High-pressure gear pump according to claim 6,

characterized by a tubular rivet 41 whose flange 42 retains the sheet metal ring 36 during the assembly thereof.

8. High-pressure gear pump according to claim 1,

characterized in that the pressure pistons 43 consist of plastic material and comprise a stud 45 being equipped with slots 44 and a collar 46, and in that the bore 47 of the control piston 10 receiving the stud 45 is provided with a projection 48 locking behind the collar 46, as well as with a groove 50 in which engages a cam 49 disposed at the stud 45.

9. High-pressure gear pump according to claim 1,

characterized in that the control piston 10 is supported not only on the internal gear 4 but also via a collar 57 on the lateral axial disks 58 which rest with a bore on the pinion shaft 3.

10. High-pressure gear pump according to claim 9,

characterized in that the filler member bolt 62 is dis placeably positioned in the axial disks 58 and in that said axial disks 58 are suspended on a pin 59.

11. High-pressure gear pump according to claim 9',

characterized in that the collar 57 is rendered elastic by means of a perforation or aperture 56 in the control piston.

12. High-pressure gear pump according to claim 9,

characterized in that the part 72 of the axial disks 58 against which the control piston 10 bears or abuts is provided elastic by means of a slot 71 which changes over into a bore 70.

13. High-pressure gear pump according to claim 9,

characterized in that the filler member 5, when new,

has a slightly greater outside diameter than necessary so that the internal gear 4 being pressed on by the control piston 10 initially runs up on the filler member before the axial disk 59 is supported on the pinion shaft 3.

14. High-pressure gear pump according to claim 1,

characterized in that the axial disks 73 are positioned on the pinion shaft 3 and comprise a bore into which a pin 74 engages, said pin being positioned in the control piston 10.

15. High-pressure gear pump according to claim 1,

characterized in that the pin 74 engages with an extension 87 into a bore of the housing cover 83 and is equipped in the bores of the control piston 10 and of the housing cover 83 with a collar 86, 89, and in that it has within the area of the extension 87 a reduction of the cross sectional area.

16. High-pressure gear pump according to claim 1,

characterized in that the axial disks 91 are rotatably positioned on the pinion shaft 3 and are connected by means of a cylindrical pin 92 with the filler member 5, the aggregate 5, 91, 92 thus formed being supported against a housing pin 93 being secured in the housing.

17. High-pressure gear pump according to claim 16,

characterized in that the filler member 5 is flattened at its thicker end 94 and rests or bears against the equally flattened but otherwise cylindrical housing pin 93, the latter being movably positioned in bores of the axial housing parts.

References Cited UNITED STATES PATENTS 1,719,639 7/ 1929 Wilsey. 3,273,502 9/1966 Martz. 3,289,599 12/1966 Eckerle et al. 3,315,608 4/ 1967 Eckerle. 3,315,609 4/1967 Eckerle.

DONLEY J. STOCKING, Primary Examiner W. J. GOODLIN, Assistant Examiner US. Cl. X.R. 418-71, 169

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