PNEUMATIC MOTOR ASSEMBLY FOR A LUBRICANT PUMP

Abstract: A pneumatic motor (9) assembly for a lubricant pump comprises a body (15), which forms a cavity (16) supplied with compressed air, a first hole (18) and a second hole (19) which are formed axially on the side wall of the cavity, a stem (20), which is slidingly accommodated in the first (18) and second holes (19) and supports, at one end, a piston (21) which moves in a cylinder (8) associated with the body and, at the other end, cooperates with the riser (10) of the pump; an exchanger means (24) is accommodated in the cavity (16) and is provided with an axial through hole (25) which slidingly accommodates a narrow intermediate portion (26) of the stem (20); a means for diverting the air is associated with a front opening of the cavity and interacts with the exchanger means; and an elastic means (130) cooperates laterally with the exchanger means (24); the axial through hole includes a wider end portion, which is directed toward the end of the stem that is provided with the piston and accommodates a non-narrow part of the stem during the return stroke of the piston; the elastic means is arranged between the exchanger means (24) and the side wall (17).

Description: PNEUMATIC MOTOR ASSEMBLY FOR A LUBRICANT PUMP The present invention relates to a pneumatic motor assembly for a lubricant pump, which is used particularly in the field of maintenance and repair of vehicles such as cars, vans, trucks, tractors, et cetera. The background art is constituted by a pneumatic motor assembly, for lubricant pumps, comprising a body that forms a cavity supplied with compressed air. A first hole and a second hole are formed axially in the side wall of the cavity. The holes slidingly accommodate a stem. The stem supports, at one end, a piston that moves in a cylinder that is associated with the body and cooperates, at the other end, with the riser of the pump. An exchanger means is accommodated inside the cavity and is provided with an axial through hole, which slidingly accommodates a narrow intermediate portion of the stem. The exchanger means cooperates frontally with a means for diverting the air, which is associated with a front opening of the cavity and is laterally associated with an elastic means. In particular, the cooperation between the exchanger means and the elastic means is provided by two levers, which are pivoted between the side walls of the body and the front faces of two bushes slidingly inserted in holes provided laterally in the body. The elastic means acts on the rear faces of the bushes and is constituted by two spiral springs. The springs are accommodated in two caps, which are screwed by virtue of one end to the holes formed laterally in the body. The operation of such motor assembly is as follows. Assume, for example, that the piston is performing its forward stroke inside the cylinder. Initially, the exchanger means is in a retracted position. The air is introduced in the cylinder so as to move the piston through a hole provided to the rear in the cavity, the diverting means and a passage that runs within the body and leads to the bottom of the cylinder. Correspondingly, the air contained in the chamber, whose volume is gradually reduced by the piston, is discharged externally through the diverting means. The exchanger means moved by the stem reaches the inversion position from the retracted position, and from that position it is moved to the forward position by the intervention of the elastic means. In this transfer, the exchanger means acts on the diverting means so as to block the intake and outlet, preparing them for the return stroke of the piston. In this case, the air is introduced through the usual hole, the diverting means and the pipe for connection to the top of the cylinder. Correspondingly, the air contained in the chamber, whose volume is gradually reduced by the piston, is discharged externally through the passage and the diverting means. The exchanger means, entrained by the stem, again reaches the inversion position from the forward position. From the inversion position it is moved to the retracted position by the intervention of the elastic means. During this transfer, the exchanger means acts on the diverting means so as to block the intake and the outlet, preparing them for the new forward stroke of the piston, and so forth. The reciprocating movement of the stem aspirates the lubricant, which by rising up the riser becomes available for dosage. The main drawback of the above described motor assembly is its performance, which is highly impaired by the fact that the stroke available inside the cylinder is not utilized completely by the piston. In fact, during the return stroke, the piston stops before it reaches the bottom of the cylinder. This is due to the fact that the narrow portion of the stem is necessarily longer than the exchanger means. Therefore, during the forward stroke of the piston, the narrow portion of the stem protrudes partially with respect to the bottom of the cylinder. Accordingly, it is necessary to prevent the variation in diameter that occurs between the narrow portion and the rest of the stem that lies outside the bottom from interfering with the annular gasket arranged so as to wrap around the stem on a guiding and sealing bush associated with the first hole of the cavity that is directed toward the cylinder. For this reason, a bush of considerable height is currently used and in turn prevents the piston from reaching the bottom at the end of its return stroke. Furthermore, within the scope of this main drawback it is noted that this actuation of the cooperation between the exchanger means and the elastic means is particularly complicated and therefore expensive. Moreover, the lateral protrusions formed by the caps worsen the overall aesthetic appearance of the assembly. A second drawback of conventional devices is that they comprise a means, for guiding and sealing the stem toward the riser, constituted by a guiding bush, an annular gasket and a closure flange, packed and inserted in a compartment formed axially in the body, just below the cavity, and retained by an elastic end ring engaged in the compartment. Accordingly, the lubricant delivery hole is provided just below the compartment. This entails that the axial dimension of the body is particularly large. Since the body is normally made of aluminum, a material that is notoriously valuable and therefore expensive, the purchase costs of the raw material are rather onerous and have a considerable effect on selling prices of the end products. Furthermore, the number of machine-tool treatments required to obtain the finished assembly is particularly large, thus increasing production costs. The body of the assembly is in fact obtained from a solid cylindrical block, which is initially provided with an axial bore having different diameters and so forth, accordingly also entailing considerable machining waste. The aim of the present invention is to overcome the drawbacks noted in the prior art, by providing an improved pneumatic motor assembly for a lubricant pump that in particular improves appreciably the operating efficiency and reduces its manufacturing costs in relation to the material used and to the number of machining treatments required, so as to contain the final cost. Within this aim, an object of the invention is to provide a motor assembly that is highly compact. This aim, this object and others that will become better apparent hereinafter are achieved by a pneumatic motor assembly for a lubricant pump as claimed in the accompanying claims. Further characteristics and advantages of the invention will become better apparent from the description of a preferred embodiment thereof, illustrated only by way of non-limitative example in the accompanying drawings, wherein: Figure 1 is a perspective view of a lubricant pump provided with the assembly according to the invention; Figure 2 is a partially sectional exploded view of the assembly; Figure 3 is a sectional view, taken along the line Ill-Ill of Figure 2, of a detail of the assembly; Figure 4 is a sectional view, taken along the line IV-IV of Figure 2, of another detail of the assembly; Figure 5 is a sectional view of the assembly, taken along a meridian plane that passes through its longitudinal axis; Figure 6 is a detail sectional view of the assembly, taken along a meridian plane that passes through its longitudinal axis; Figure 7 is a detail sectional view, taken along the line VII-VII of Figure 6, of the assembly in the unassembled condition; Figure 8 is a detail sectional view, taken along the line VII-VII of Figure 6, of the assembly in the assembled condition. With reference to the accompanying figures, and initially to Figure 1 , the pump, generally designated by the reference numeral 6, is applied vertically to a drum 7 containing liquid or semisolid lubricant. The pump 6 is substantially axially elongated and includes, in the following order, a pneumatic cylinder 8, a motor assembly 9, and a riser 10. The riser is rigidly associated with the lid 11 of the drum 7. The pump 6 receives compressed air through a hose 12 and dispenses the lubricant through a hose 13, which has, at its free end, a dosage gun 14 that can be operated manually. The motor assembly 9 includes a body 15 that is predominantly axially elongated. The body 15 forms a cylindrical cavity 16, which lies approximately at right angles to the length of the body 15. The cavity 16 is fed with compressed air through a hole provided at the rear (not shown) for connection to the hose 12. A first hole 18 and a second hole 19 are provided on the side wall 17 of the cavity 16, along the main axis of the body 15. A stem, generally designated by the reference numeral 20, slides within the holes and supports, at one end, a piston 21, which moves inside the cylinder 8 and cooperates with the riser 10 at the other end. The stem 20 is formed in two portions 22 and 23, which are mutually joined by virtue of a screw coupling. An exchanger means 24 is accommodated inside the cavity 16 and is provided with an axial through hole 25, which slidingly accommodates a narrow intermediate portion 26 of the stem 20. The narrow intermediate portion 26 is formed in the end part of the portion 22 that lies opposite to the one provided with the piston 21. At the end of the narrow intermediate portion 26 there is a short threaded part 27, which is engaged in a corresponding complementarily threaded hole 28 formed at the end of the portion 23, so as to form the screw coupling. An elastic means, generally designated by the reference numeral 29, cooperates laterally with the exchanger means 24 by virtue of levers 30 engaged in slots 31 formed on the side wall of the exchanger means 24. A diverting means D introduces air from the cavity 16 first into one chamber of the cylinder 8 and then into the other chamber, the chambers being formed by the piston 21, and evacuates externally the air contained alternately in each one of the chambers, whose volume is gradually reduced by the piston 21. The diverting means D is associated with a front opening of the cavity 16 and interacts with the exchanger means 24 by virtue of a flat region 32 formed at the front on the exchanger means. The particularity of the motor assembly 9 is that the axial through hole 25 comprises a wider end portion 33, which is directed toward the end of the stem 20 that supports the piston 21 so as to accommodate a non-narrow part of the stem 20 during the return stroke of the piston 21 , thus delaying the exchange. In this manner, the stroke of the piston shifts toward the return to an extent that is equal to the depth of the wider portion 33. As shown in particular in Figure 5, by virtue of the wider portion 33 the stem 20 in fact penetrates more deeply into the exchanger means 24. Again with reference to Figure 5, the non-narrow part, designated by the reference numeral 34, is located directly behind the narrow portion 26 in the direction of the return stroke of the piston 21. Accordingly, the length of the non-narrow part 34 is equal to the depth of the wider end portion 33. The limit of the return stroke of the piston 21 is determined by the locator 35, which is formed between the wider end portion 33 and the axial through hole 25, which constitutes an abutment with respect to the corresponding locator 36 formed on the stem 20 so as to straddle the narrow intermediate portion 26 and the non-narrow part 34. The above feature allows to use a guiding and sealing bush 37 associated with the first hole 18 which has a limited height, so as to not interfere with the return stroke of the piston 21. Furthermore, such feature allows to avoid the problem of the escape of the locator 36 from the gasket 38 provided on the guiding and sealing bush 37, although the bush has a limited height. The locator 36 in fact always lies behind the conventional assemblies during the forward stroke of the piston 21 , and for this reason it does not interfere with the gasket 38. The base of the guiding and sealing bush 37 acts as an abutment for the exchanger means 24 in the advanced position. For a good operation of the assembly 9, it is also necessary to provide a slight elongation of the exchanger means 24 on the part directed toward the riser 10. This ensures a sufficient resting surface between the exchanger means 24 and the stem 20 during mutual sliding. Accordingly, the narrow intermediate portion 26 is also extended by the same length, so as to restore the proportions between the axial dimensions of the components that interact. With the exchanger body 24 and the stem 20 thus modified, the other locator 39 formed on the stem 20 would interfere with the guiding and sealing means used on the side of the riser 10 in conventional devices. Therefore, it would be necessary to further lengthen the body, but this would entail obvious new increases in the costs of raw material. In order to obviate all this, the assembly 9 includes a guiding and sealing cartridge 40, which is engaged in the second hole 19, protrudes along the stem 20 outside the body 15, and is directed toward the riser 10. The cartridge 40 is formed by a first tubular segment 41, which is provided externally with a threaded end part 42, which is engaged in the corresponding second complementarily threaded hole 19, and is provided internally with a likewise threaded intermediate part 43. The head of the first segment 41 acts as an abutment for the exchanger means 24 in the retracted position. A second shorter tubular segment 44 is arranged coaxially inside the first tubular segment 41 and is externally provided with a threaded end part 45, which engages the corresponding threaded intermediate part 43 of the first tubular segment 41. Internally, the second tubular segment 44 has, at the threaded end part 45, a hexagonal seat 46, which accommodates a handling tool (not shown) for screwing and, at the opposite end, has an annular gasket 47, which is adapted to form a seal on the portion 23 of the stem 20 against air seepage from the cavity 16 toward the riser 10. In order to avoid seepages of lubricant in the opposite direction, an annular gasket 48, having an inverted U-shaped cross-section, is inserted in the first tubular segment 41 on the side of the riser 10, just below the second tubular segment 44. Also, in order to avoid any wavering of the piston 21, at the beginning of its forward stroke, it is possible to provide a secondary chamber 49 formed in the bottom of the cylinder 8. With particular reference to Figures 6, 7 and 8, an elastic means, generally designated by the reference numeral 130, cooperates laterally with the exchanger means 24 as a replacement of the conventional means shown in the other figures. A particularity of the elastid means 130 is that it is arranged between the exchanger means 24 and the side wall 17. The elastic means 130 is constituted by two springs 131, shown in Figure 7. Each spring 131 includes two legs 132, two arms 133, and a central concavity 134, which in the active condition is directed into the cavity 16. Figure 7 shows that, before assembly, the legs 132 are divaricated, whereas after assembly the legs 132 are substantially parallel. Accordingly, before assembly, the legs 132 form an obtuse angle with the arms 133 and in the active condition they form a substantially right angle. The legs 132 of each spring 131 are inserted in seats 135 and 136 formed respectively in the exchanger means 24 and in the body 15. More specifically, the seats 135 formed in the exchanger means 24 include two holes 137 in which elastic pins 138 are inserted. The holes 137 are formed in the sides of the exchanger means 24 in the central area of the flat region 32, symmetrically and at right angles to the longitudinal central axis of the exchanger means 24. The seats 136 formed in the body 15 include two holes 139, in which elastic pins 140 are inserted. The holes 139 are formed on the margin of the cavity 16, in the central band of the body 15, symmetrically and at right angles to the longitudinal central axis of the body 15. The holes 139 include a first portion 141 and a second portion 142. The first portion 141 of the holes 139 has a larger diameter than the second portion 142. In this manner, during the drilling of the holes 139 straight grooves, equal in length to the first portions 141 , are formed on the side wall 17, allowing to position the springs 131. The springs 131 are kept in position by pins 143, inserted in the first portions 141 after the springs 131 have been arranged in the active position. The pins 143 are in turn retained within the first portions 141 by the diverting means D, which closes the front opening of the cavity 16. The springs 131 are preferably made of a metal wire shaped so as to lie on a plane. With reference to the accompanying figures, the general operation of the assembly 9 is per se known. The operation of the elastic means 130 occurs as follows. Assume that the exchanger means 24 is in one of the two stroke limit positions. Moving from this position, the exchanger means 24 compresses the springs 131 until it reaches the position in which the diverting means D reverses the flow of the circulation of the air. From this position, the springs 131 are released, pushing the exchanger means 24 to the other stroke limit position, and so forth. As described above, the improved pneumatic motor assembly achieves the intended aim and object, allowing an actual improvement in efficiency owing to the fact that the stroke available in the cylinder is utilized fully by the piston, both during the forward stroke and during the return stroke, and it allows to reduce manufacturing costs and accordingly the final price, and to improve its overall aesthetic appearance. Furthermore, the guiding and sealing cartridge external to the body allows a considerable saving of material thereon which is approximately equal to 20%, because the portion of body related to the compartment for accommodating the means for guiding and sealing the stem on the riser side is no longer necessary, and because the lubricant dispensing hole is formed directly below the cavity instead of below the guiding and sealing means. The same solution allows to use tubular segments instead of solid cylindrical segments in order to form the body. This feature allows to save on the purchase of raw material and allows a considerable reduction in the number of operations of the manufacturing cycle. For example, it is noted that the first and second holes have the same diameter and are equally threaded. Furthermore, according to the invention, it becomes possible to use a single body for a wide variety of pumps. The solution adopted to provide the seats helps to reduce costs. Instead of providing very small holes in order to insert the legs of the springs, it is in fact more convenient to provide holes having a larger diameter and then insert therein elastic pins so as to bring the holes to the required diameter. The solution chosen for fitting the springs is also relevant, since it proves itself very easy. It is in fact sufficient to place the body at the end of its stroke, take each spring by compressing its legs until they are parallel, and then insert them in the already-provided seats. In practical execution, the materials used, the shapes, the dimensions and the constructional details, may be different from the ones described herein but technically equivalent thereto without thereby abandoning the scope of the invention.

Claims: CLAIMS 1. A pneumatic motor assembly for a lubricant pump that comprises a body, which forms a cavity supplied with compressed air, a first hole and a second hole formed axially on the side wall of said cavity, a stem, slidingly accommodated in said holes and supporting, at one end, a piston moving in a cylinder associated with said body and, at the other end, cooperating with the riser of said pump; an exchanger means, accommodated in said cavity and provided with an axial through hole slidingly accommodating a narrow intermediate portion of said stem; a means for diverting said air, associated with a front opening of said cavity and interacting with said exchanger means, and an elastic means which cooperates laterally with said exchanger means, characterized in that said axial through hole comprises a wider end portion, directed toward said end of said stem that is provided with said piston and accommodating a non-narrow part of said stem during the return stroke of said piston; and in that said elastic means are arranged between said exchanger means and said side wall. 2. The assembly according to claim 1, characterized in that said non-narrow part is located directly behind said narrow portion along the return stroke of said piston. 3. The motor assembly according to one or more of the preceding claims, characterized in that said exchanger means comprises a locator formed by said wider end portion and by said axial through hole, said locator forming an abutment for the corresponding locator formed on said stem astride said narrow portion and said non-narrow part. 4. The motor assembly according to one or more of the preceding claims, characterized in that said exchanger means comprises an extension toward said riser and in that said narrow intermediate portion comprises an extension equal to said extension of said exchanger means. 5. The motor assembly according to one or more of the preceding claims, characterized in that it comprises a guiding and sealing bush, screwed into said first hole and protruding moderately into said cylinder so as to not interfere with said return stroke of said piston. 6. The motor assembly according to one or more of the preceding claims, characterized in that it comprises a guiding and sealing cartridge, rigidly coupled to said second hole and protruding along said stem outside said body toward said riser. 7. The motor assembly according to one or more of the preceding claims, characterized in that said cartridge comprises a first tubular segment, externally provided with a threaded end part that engages said second complementarily threaded hole and is internally provided with a threaded part. 8. The motor assembly according to one or more of the preceding claims, characterized in that said cartridge comprises a second tubular segment, internally coaxial to said first segment, and shorter than said first segment, said segment being externally provided with a threaded end part that engages in said complementarily threaded part of said first segment and is internally provided, at said threaded end part, with a hexagonal seat for accommodating a handling tool for screwing said second segment into said first segment, and is provided, on the side of said riser, with an annular gasket for providing a seal on said stem against seepages of air from said cavity to said riser. 9. The motor assembly according to one or more of the preceding claims, characterized in that said cartridge comprises an inverted U-shaped annular gasket, inserted in said first segment on the side of said riser just below said second segment and preventing seepages of lubricant from said riser into said assembly. 10. The motor assembly according to one or more of the preceding claims, characterized in that it comprises an annular secondary chamber formed in the bottom of said cylinder. 11. The motor assembly according to claim 1 , characterized in that said elastic means comprises a pair of springs. 12. The motor assembly according to claim 11 , characterized in that each one of said springs comprises two legs, two arms and a central concavity directed toward said cavity. 13. The motor assembly according to claim 12, characterized in that before assembly said two legs are divaricated and in the active condition said two legs are substantially parallel. 14. The motor assembly according to claim 12, characterized in that before assembly said two legs and said two arms form an obtuse angle and in that in the active condition said two legs and said two arms form a substantially right angle. 15. The motor assembly according to claim 12, characterized in that said legs are inserted in seats formed respectively in said exchanger means and in said body. 16. The motor assembly according to claim 15, characterized in that said seats of said exchanger means comprise two holes and two elastic pins inserted in said pair of holes. 17. The motor assembly according to claim 16, characterized in that said holes in said exchanger means are formed in the central area of a flattened region, in a symmetrical position and at right angles to the longitudinal central axis of said exchanger means. 18. The motor assembly according to claim 15, characterized in that said seats of said body comprise two holes, each divided into a first portion and a second portion, and two elastic pins, inserted in said second portions of said holes. 19. The motor assembly according to claim 18, characterized in that said first portion has a larger diameter than said second portion. ' 20. The motor assembly according to claim 18, characterized in that said holes in said body are formed in the central band of said body, symmetrically and at right angles with respect to the longitudinal central axis of said body. 21. The motor assembly according to claim 19, characterized in that said first portions of said holes affect said side wall so as to form straight grooves which allow to insert said springs in said pins inserted beforehand in said second portions. 22. The motor assembly according to one or more of the preceding claims, characterized in that said springs are held in position by two pins inserted in said first portions, said pins being in turn held in position by said diverting means. 23. The motor assembly according to one or more of the preceding claims, characterized in that said springs are formed by at least one wire shaped so as to lie on a plane.

Inventors: ROSA VALERIO, ROSA, VALERIO
Applicants: ROSA VALERIO, ROSA, VALERIO
Application year: 2001
Main classification: F16K31
IPC codes: F04B9, F04B53, F16K31, F16N13