MXPA97010509A - Tri-lobed cam engine - Google Patents

Abstract

En una máquina (10) que tiene pistones alternos flotantes (40) cada uno con un rodillo seguidor de leva (46) que descansa en una leva de tres lóbulos (20), cada seguidor de leva estásoportado por un cojinete guía (50) que corre sobre una pista (54) que sirve para transmitir a la pista componentes de fuerza reactivas laterales generadas entre la leva y el rodillo seguidor de leva.

Description

THREE-BED CAM MACHINE FIELD OF THE INVENTION The invention relates to an alternate piston machine that includes a three-lobed cam for converting reciprocating piston movements to a rotary movement or vice versa, depending on whether the machine is used in a motor mode or in a motor mode. compressor.

BACKGROUND OF THE INVENTION The reciprocating three-piston cam machine is developed in the following patents: Patents of the United States of North America Numbers: 793,270; 1,765,237; 1,792,062; 1,825,417; 2,124,604; 4,697,552; 4,727,749; 5,035,221; 5,281,104 and French Patent 2,037,132 In each of the mentioned patents there are installed a pair of diametrically opposed pistons which are coupled together in a pushing and pulling relationship by a joint that is not extensible. Each piston has a cam follower roller, the link serving to keep the cam follower rollers in contact with the cam in all rotational positions thereof. The coupling of the pistons together in this mode requires a three-lobed cam shape so that the dimensions between the two diametrically opposed portions are substantially constant. Generally king, such a form includes a flattening of the lobes of the cam and the formation of a concavity between the pairs of adjacent lobes. These machines have a relatively large angular range so they can not be activated automatically when they are operated as external combustion engines. In U.S. Patent No. 1,203,855 a three-lobed cam machine is described where the pistons are not connected together, and therefore are floating freely. The cam of this machine is asymmetrically molded, so the machine would be suitable for one-way operation only. In addition, the interaction between the cam follower rollers and the cam would generate a severe reactive force which forces the piston to make contact with the cylinder wall with which it alternates, causing rapid wear. An object of this invention is to provide an improved three-lobed cam machine. It is another object of the invention to provide a three-lobed camming machine that utilizes free-floating pistons where the interreactive forces between the piston and the cylinder wall are reduced. There is still another object of this invention to -tf -? = - ái-i-M-M-IMI-. provide the three-lobed cam machine where the cams of different profile can be replaced without requiring another change that varies the characteristics of the machine. Still another object of the invention is to provide a three-lobed cam machine having a simple modular construction in which the number and size of the cylinders can be easily modified. Yet another object of the invention is to provide a three-lobed cam machine that can be activated by itself when operating in external combustion engines.

SUMMARY OF THE INVENTION According to one at of the invention, a machine comprises a crankcase with a camshaft and a cam with three lobes and four free floating piston elements arranged in the crankcase with a ratio of equal separations. Each piston member includes a cylinder and a free floating piston for a reciprocal movement between the cylinder and the cam follower roller associated with each piston. The cam follower roller has associated therewith a guide bearing element and the crankcase has a track element along which the guide bearing element is movable. The guide bearing element serves to reduce piston and cylinder wear, íMñ ¡> -m * ¡^ mmi transmitting to the track element the reactive forces generated in the cam follower roller by the cam, which would otherwise force the piston into contact with its cylinder. Preferably, the guide bearing element includes a pair of guide bearings arranged on axially opposite sides of the cam follower roller, the axial direction of the machine, which is considered to be that of the camshaft of the machine. Also preferably, the guide bearing elements and the cam follower roller conveniently have a colinear rotation axis. With the reduction of the piston-cylinder interaction and with the sliding movement of the cam follower roller and the associated guide bearing elements, the machine is particularly adapted to use it as a high torque, essentially an air motor, without oil, for use in food processing businesses. According to the preferred embodiment, the four piston elements are arranged to form two diametrically opposed pairs. The cylindrical axes of the pairs of cylinders intersect with the axis of the camshaft of the machine and this is to provide a symmetry and reversibility of the machine direction. Suitable for general purposes of use of the machine, the cam element has the shape of an equilateral triangle, whose sides are essentially rectilinear. The lobes of the cam element are relatively rounded with an appropriate radius of approximately 6 millimeters (0.25 inches), said machine, when operating as an external combustion engine, can be self-starting and reversing. However, the shape of the cam element will influence the torque and other characteristics of the machine, and under appropriate circumstances, a triangular cam member formed with undulating sides may be preferred, particularly when the sides have a convex shape in the proximity of the lobe of cam. Further in accordance with the preferred embodiment, the crankcase is provided with eight apertures symmetrically arranged around it and conveniently each aperture has an associated track element. Four of the openings can be closed with the above mentioned piston element, which can be referred to as the primary piston element, with the remaining four openings uncovered. Such a machine is easily modified to form an eight-cylinder machine only by removing the lids and replacing them with secondary piston elements that are essentially identical to the primary piston elements. The following objects and aspects of the invention, together with other objects, aspects and advantages thereof may be better appreciated with the consideration of the The following description of the preferred modalities thereof, taken in conjunction with the drawings appended hereto.

BRIEF DESCRIPTION OF THE DRAWINGS IN THE DRAWINGS: Figure 1 is a schematic cross-sectional view of the middle section of a four-cylinder machine according to the invention; Figure 2 is an axial schematic view of the middle section through one of the cylinders of the machine of Figure 1, with valve components further shown; Figure 3 is a schematic axial elevation showing more details of the valve arrangement with the hidden detail shown in dotted line; Figure 4 is a plan view of the cylinder of Figure 3; Figures 5 and 6 are similar to Figures 3 and 4, respectively, but show a modified cylinder, - Figure 7 is similar to Figure 1 but shows the eight-cylinder shape of the machine; Figure 8 is a schematic illustration of the arrangement of an electrically operated valve associated with a cylinder, and Figures 9A through 9C show variants of ^^ i ^ A cam element for use with the machine of Figure 1, with a basically triangular shape, is shown in dotted line for comparison purposes.

DESCRIPTION OF THE PREFERRED MODALITY The machine 10 comprises a crankcase 12 including a pair of opposite separated side plates 14, with a camshaft 16 assembled thereon by rotation bearings 18. A cam 20 is assembled on the camshaft 16 to rotate therewith. The casing 12 includes eight facets forming supports 22 arranged in a ratio of equal spacing in a circle centered on the axis of rotation of the camshaft 16, with stiffening spacers 26 which are positioned between the side plates 14 on each pair of adjacent supports. . A piston element 28 which includes a cylinder 30 which is placed on the alternating supports 22 and secured thereto by the bolts 32 which are conveniently screwed on the side plates 14 those supports 22 that do not have a cylinder disposed therein are generally closed by a cover 34. The piston member 28 also includes a piston 40 from which a piston rod 42 is rigidly dependent. Each piston rod 42 has a fork opening 44 in which a cam follower 46 is assembled on a bearing rod 48 adjacent to the distal end of the piston rod. ? * & r *. . , ¿Sutm. ^ ¿^ I « The bearing rod 48 projects outwards on opposite sides of the fork opening 44 to provide a support for a pair of guide bearings 50 positioned on the axially opposite sides of the cam follower roller 46. Each support 22 has associated with the same a pair of tracks 54 which are conveniently machined into side plates 14 and along which the guide bearings 50 will roll as soon as a piston 40 alternates with its cylinder 30. It will be understood that those cylinders 30 and tracks 54 and rods 10 of the bearings 48 are all centered in diameters passing through the axis of rotation of the camshaft 16. The machine 10, wherein the shape of an external combustion engine includes a valve assembly 60 conveniently in the form of a swinging inlet valve 62 operated by a push rod assembly 64 disposed outside the crankcase 12 in association with each cylinder 30 and which in a push rod 66 operated by a timing valve cam 68 arranged in the camshaft of the machine 16 and secured thereto by a key 70. an exhaust hole 72 is disposed in the wall of each cylinder 30 and an entrance door 74 in the head thereof. The cam 20 is generally in the form of an isosceles triangle with rectilinear sides 80 and lobes 82 which are sharply rounded with a radius 84 of approximately 6 millimeters, whose dimension can be relatively independent of the size of the cam 20, at least over the range where the sides 80 have a dimension in the range of approximately between 5 centimeters to approximately 50 centimeters (from 2 inches to 20 inches). The timing cam 68 has a shape that is generally complementary to that of the main cam 20, that is: it has the shape of an isosceles triangle, albeit with the lobes 86, thereof substantially flattened as will be discussed subsequently. Considering the machine 10 operating as a motor of a source (not shown) of expandable gas, and differentiating the cylinders 30 for purposes of the following description with the letters A, B, C and D, and with the components in their relative positions as shown in Figure 1, when starting, assuming that the cam of the machine valve 68 must be adjusted to provide a clockwise movement of the camshaft 16. The piston 40 of cylinder A will be marginally up to more beyond its central neutral position. The inlet valve 62 to cylinder A will be marginally open and those of cylinders B, C and D will be closed. In accordance with the foregoing, the piston 40 of the cylinder A will be forced in a downward vertical movement by the expandable gas introduced into the cylinder A, causing the cam 20 and the camshaft 16 with them to rotate in the clockwise direction of the hands. clock . The valve 62 to the cylinder A will be most conveniently close when the piston 40 of the cylinder A has descended approximately one-third of its stroke, with lobes 86 which have been formed in accordance with the above.

In concomitance with the downward movement of the piston in cylinder A, the piston of cylinder B will be forced upwards, trapping a volume of gas in the cylinder. Finally, the piston 40 of the cylinder B will assume the position of the piston 40 of the cylinder A illustrated in Figure 1 and the expandable gas will be introduced in the cylinder B. At this moment the machine will be operating dynamically, and a work output will be generated by the piston 40 of both the cylinder A, as it moves towards the bottom in its stroke, and the piston of the cylinder B. The pistons of the cylinders C and D will operate in a manner analogous to the pistons A and B and, in general, when the machine 10 is dynamically operating as a motor, two adjacent pistons will provide power in an expansion stroke and two of the adjacent pistons will be driven by the cam 20. In view of the producing a relatively high torque from the machine 20, the camshaft 16 can often be coupled directly to a unit to be operated without any intermediate distributor box, when it is desired that the machine of Figure 1 be operated on Counterclockwise direction, it is simply required to change the synchronizer cam 68 by 180 °. It will be understood that other, somewhat more complex variations can be used to change the timing cam 68 related to the camshaft 16 to reverse the direction of the rotation of the machine. Now considering the valve cam 68 to be adjusted to operate the machine 10 as a motor, which rotates in the opposite direction to the clockwise and considering that the parts are in the relative positions as seen in Figure 1, in the moment of starting the piston of the cylinder A will be in a position marginally before the center of the neutral and the inlet valves 62 to the cylinders A, C and D will be closed. The inlet valve 62 to the cylinder B will be open, forcing the piston 40 thereof to descend vertically, whereby the cam 20 is caused to rotate in a counterclockwise direction and, with it, the tree of cams 16. When the cam 20 has been rotated to a position to force the piston 40 of cylinder A to the center position of the dead center, the inlet valve 62 of cylinder A will open and the sequence of operations described above in relation with the machine when operating in the clockwise direction it is repeated in reverse.

The rolling action of the cam follower roller 46 and the guide bearings 52 and the reduction of lateral forces on the pistons 40 allows the machine 10 to be operated under certain conditions without lubrication, or with lubrication provided only by using sealed bearings , which is highly advantageous under adverse conditions. The maintenance of the machine 10 is particularly facilitated due to the free floating action of the pistons 40, which allows the cylinders 30 and the pistons 40 to be removed simply by removing the bolts 32. The cylinders 30 in accordance with the above, can to be replaced by cylinders 130, for example, as seen in Figures 5 and 6, which have an internal diameter substantially greater than the cylinders 30. In this instance, the safety pins 132 will not intersect the side plates 14 of the crankcase 12 Accordingly, the cylinders 130 are supported by the supports 22 by means of a pedestal 133 having an internal diameter smaller than that of the cylinder 130, whereby the bolts 32 passing through a flange turned towards 135 outside serve to secure the cylinder to the crankcase 120 in the place of a cylinder 30. The conversion of the machine 10 to an eight cylinder machine is likewise simple, involves removing the caps 34 from the machine 10 of Figure 1 and securing the cylinders 30 and their related components in place., to form the machine 110 of Figure 7. A four-cylinder engine 10 will have the power of twelve strokes per revolution of the camshaft 16, and this will be bent by the eight-cylinder engine 110. In accordance with the above, it will be appreciated that this results in engines that have an exceptionally high torque and smooth operation. Although the construction materials of the machine are not critical, much of the structure thereof, including the crankcase 10 is particularly amenable to being manufactured from plastic materials, and contemplates the possibility that the tracks 54 are coated with replaceable coatings 56 to facilitate maintenance. As seen in Figure 8, the machine of the invention can have the assembly of an electrically operated valve 160 associated with each cylinder 130, which takes the place of the mechanically operated valve assembly 60 described above. The valve assembly 160 includes an associated switch mechanism 162, which includes the switch contacts 164a, 164b, which are ignited by a rotor 120, and a reverse switch 166 which allows the selection of either of the two contacts of switch 164a and 164b. Now, with reference to Figure 9A, a second embodiment of the main cam 20 is identified therein with the number 12OA, with the equilateral basic form, with rectilinear sides, the shape similar to that of the cam 20 which is superimposed on the dotted lines denoted by the letter O. Cam 120A has lobes 182 and sides 180 extending between adjacent pairs of lobes. The sides 180 include a first portion 181A extending between a lobe and a middle zone denoted by the letter M, and a second portion 183A extending between the middle zone and the adjacent lobe. In this second embodiment, the lateral portions of the cam 181A and 183A are formed in an identical manner whereby the sides 180 are completely symmetrical, and the cam 120A can rotate in any direction. Assuming a counterclockwise direction, the side portions of the cam 18IA will control the movement of a piston like the piston 40 in the power stroke of the machine, and the side portions of the cam 183A will control the movement in the escape race. The portion 181A has a flattened S shape, which is initially a convex curve; this has the effect of reducing the acceleration of the piston 40 in the vicinity of the lobe 182 in the power stroke relative to the acceleration produced by using the cam 20; this also has the effect of flattening the output of the torque curve whereby maximum torque output occurs in the interval after the exit stroke, while being held over the increased range. The lateral portion of the cam 181A changes to a concave shape in the vicinity of the middle zone M, said area being disposed closer to the center of rotation of the cam 120A than in the corresponding cam 20. This has the effect of increasing the length of the power stroke and also the angular range over which a relatively high output of torque is maintained in the output stroke. The side portion of the cam 183A also has the shape of a flattened S. Since a certain amount of gas will be trapped inside the cylinder to serve as a cushion to a piston inside this cylinder in the exhaust stroke and that the gas will be compressed by an applied force through a piston follower like 46. This portion lateral cam 183A serves to place the angular interval over which the maximum force is applied generally in diametric opposition to that on which a maximum torque is produced from another cylinder of the machine, to assist in the operation of smoothness of the same It will also serve to decrease the deceleration of a piston when approaching the lobe 182 in the exhaust stroke. A cam having the shape shown in Figure 9A may be preferred for moderately high moderate speed reversible machines 10. However, it will be appreciated that other cam shapes may be preferred, for example, that shown in Figure 9B, wherein, the initial portion 181B of the cam 120B has a flattened and neutral shape as compared to the basic triangular shape, a cam in this way is the precise one for medium speed operation. In Figure 9C a cam 120C is shown in which the initial portion has a negative inclination which is most appropriate for low speed in high torque machines. It will be appreciated that many changes can be made in the embodiment illustrated, while remaining within the scope of the invention and it is intended that said changes be covered by the claims appended hereto.

Claims (13)

1. A machine (10) comprising: a crankcase (12); a camshaft (16) assembled in said crankcase for relative rotation therewith; a three-lobed cam (20) secured to said camshaft within said crankcase; four primary piston elements (28) assembled in the crankcase in an equidistant relationship with respect to the camshaft element; each element of the primary piston comprising a cylinder (30) a piston (40) assembled for an independent alternate movement within the cylinder and a cam follower roller (46) connected to the piston; the improvement comprises a guide bearing member (50) associated with the cam follower roller; and a track element (54) supported from said crankcase along which the guide bearing element is moveable as long as the piston alternates in its cylinder; The guide bearing element serves to transmit to said track element the reactive forces generated between the cam and the cam follower roller which tends to force the piston into contact with its cylinder.

2. A machine as defined in claim 1 wherein the guide bearing member includes a pair of guide bearings respectively disposed on opposite sides of the cam follower roller.

3. A machine as defined in claim 2 wherein each cylinder has a cylinder axis which intersects the axis of said camshaft.

A machine as defined in claims 1, 2 or 3 wherein the cam follower roller and its associated guide bearing member can rotate and have a collinear axis of rotation.

A machine as defined in claims 1, 2 or 3 wherein the cam is essentially in the form of an equilateral triangle having its rounded apices with a radius of about 6 millimeters.

A machine as defined in claims 1, 2 or 3 wherein the cam member is convexly curved adjacent to each lobe on at least one side of the lobe.

7. A machine as defined in claims 1, 2 or 3 wherein the cam element is concavely curved adjacent the middle area of each side thereof and said middle area is positioned inwardly of a line interconnecting the apices of a pair of adjacent lobes.

8. A machine as defined in claims 1, 2 or 3 wherein each piston has a piston rod (42) rigidly secured thereto and the cam follower roller and the guide bearing member are assembled from the piston rod.

A machine as defined in any one of claims 1 to 6 wherein the machine has elements of four secondary pistons generally identical to the elements of primary pistons assembled from the crankcase in symmetrical relation to the elements of the primary pistons .

A machine as defined in any one of claims 1 to 9 wherein the crankcase includes a pair of opposite separate side walls (14) and wherein the track element (54) is formed as slots in the walls lateral

11. A machine as defined in claim 10 wherein the slots are provided with interchangeable coverings (56).

12. A machine as defined in any one of claims 1 to 11 wherein each cylinder has an entry port (74) and wherein the valve member (60) is associated with the entry port.

13. A machine as defined in claim 12 wherein the valve member is actuated