US1863877A

US1863877A - Internal combustion engine

Info

Publication number: US1863877A
Application number: US266494A
Authority: US
Inventors: Rightenour Asa Lee
Original assignee: Individual
Current assignee: Individual
Priority date: 1928-04-02
Filing date: 1928-04-02
Publication date: 1932-06-21
Anticipated expiration: 1949-06-21

Description

June 21, 1932.

A. L. RIGHTENOUR INTERNAL COMBUSTION ENGINE Filed April 2, 1928 5 Sheets-Sheet l June 21, 1932. RlGHTENOUR 1,863,877

INTERNAL COMBUSTION ENGINE Filed April 2, 1928 5 Sheets-Sheet 2 flaa L. Rgi iinour @MMLM Mags.

3 5 Sheets-Sheet 3 fizz 67%: lggghienour June 21, 1932- A. L. RIGHTENOUR INTERNAL COMBUSTION ENGINE Filed April 2, 1928 June 21, 1932- A. L. RIGHTE NOUR 1,863,377

INTERNAL COMBUSTION ENGINE I Filed April 2, 1928 5 Sheets-Sheet 4 kjnc'enifir' Visa L-ffz' hzenoun 1 M 2 June 21, 1932. A. L. RIGHTENOUR INTERNAL COMBUSTION ENGINE Filed April 2, 1928 5 Sheets-Sheet 5 Patented June 21, 1932 is srarss PATEN T OFFICE 1 ASA. LEE RIGHTEN'OUR, OF CHICAGO, ILLINOIS INTERNAL COMBUSTION ENGINE Application filed April 2,

operative engagement. The cam is formed with two diametrically opposed lobes having arcuate surfaces adapted to actuate the piston successively for each revolution of the cam in an intake or suction stroke, a compression stroke, a firing stroke, and an exhaust or scavenging stroke. The opposed lobes are unequal in length so that the exhausting and intake strokes are of maximum length, and substantially longer than the compression and firing strokes. The opposed lobes, also are shaped to vary the time and rate of movement of the piston in opposite directions. This may be accomplished by forming the opposed cam lobes of different transverse widths, and also by off-setting one of the contact faces on each end of the cam at a. greater distance from the longitudinal center of the cam than its opposite face. As a result, the opposite sides of each end of the cam are formed with arcs of diiferent curvatures. By reason of this construction, the cam causes a rapid preliminary movement and a subse:

quent slower movement of the pistonduring the scavenging'or exhaust stroke; causes the return or suction stroke to be slowly initiated and then accelerated to a greater speed than the maximum speed of the exhaust stroke, thereby resulting in an intense suction ac.- tion; causes the compression stroke to increase in speed during its first half and then gradually diminish to the end or firing point; and causes the firing stroke to be more rapid than the compression stroke, and then decrease. thereby resulting in the greatest leverage at the beginning of the stroke. The piston Wlll go through one complete cycle,

of movements for each completerevolution of the cam. The valves are therefore oper- DU and means for holding the two yieldingly in ated directly from the cam shaft and with-' 1928. Serial No. 266,494.

out the use of special timing mechanism and gearing. F f

By providing a full exhausting stroke and a full intake stroke, the burned gases are completely expelled from the cylinder, and a large, fresh and cool charge is taken in. As a result, no portion-of-the unburned gases remains to deposit carbon in the cylinder or to cause detonation upon contact with the incoming charge, to dilute and heat thefresh charge, and to lower the compression. Provision need not be made for taking careof high temperatures, and a relatively thinfuel mixture may be used. A high and uniform torque is obtained. By providing an actuating cam for the piston, few mechanical parts areneeded. Thus, the motor has no crankshaft, connecting rod, camshaft, connecting rod bearing, timing gears, water jacket or radiatoni i a The primary object of the present invention resides in'the provision of a novel motor of the above general type having a plurality of piston and cylinder units.

if the cylinders are spaced peripherally about the motor casing, the motor will take up a great deal of space, will be cumbersome and awkward, and will be impracticable for a great many purposes, such as farmuse.

Other important objects of the present in-- vention therefore reside in theprovision of a new and improved. motor havinga plurality of piston and cylinder. unitsin which the units are grouped at one side of the motor casing, and having means for operating the pistons in uniform sequence. 7

A further object is to provide a novel multi-cylinder motor in which the cylinders are grouped in a portion of the motor casing, and in which the pistons are adapted to be actuated by a cam having a plurality of peripherally spaced points in a multiple of two. corresponding inversely to that circumferential portion of the casing occupiedby the cylinders. a r a Still another object is to provide a multi Cylinder motor of the above characterin, which the firing strokes of the pistons, over lap so that one of the pistons is-in a 'firing stroke at all times, thereby obtaining a uniform torque, reducing vibration, and eliminating dead centers.

A further object is to provide a multicylinder motor of the above character in which there will be no knocking, and in which ball-bearings can therefore be used to advanuniform pressureat all the bearing parts,

thereby avoiding knocking and hence making the use of ball bearings practicable. 1

A further object resides'in the provision of a novel oiling system for the motor.

A general object resides in the provision of a'novel mnlti-cylinder motor of the above general type which is simple, light and inexpensive in constructlon, which comprises a relatively small number of parts, which can be readily assembled, disassembled and repaired at a relatively small cost, and whlch is hi hly eflicient in operation and adapted to a wi e range'of uses.

Further objects and advantages will become apparent as the description proceeds.

.In the accompanying drawings, Figure 1 is a' front end view of a motor embocying the features of my invention, the end plate being removed to show the interior.

Fig. 2 is a longitudinal sectional view'of the motor taken along line 22 of Fig. 1. Fig. '3 is a transverse sectional view taken along line'33 ofFig. 2.

Fig. 4 is a transverse sectional View taken along line 44 of Fig. 2.

Fig. 5 is a diagrammatic view of the actuating cam for the pistons;

Fig. 6 is an enlarged sectional View of a detail taken along line 66 of Fig. 3.

Fig. 7 is an enlarged fragmentary view in front elevation of the inner end of one of the piston and cylinder units.

Fig. 8.is a fragmentary outer end view of one of the piston and cylinder units.

Fig. '9 is an enlarged fragmentary View of a detail of the piston retaining means. 'VVhile the invention is susceptible of various modifications and alternative constructions, I have shown in the drawings and will herein describe in detail the preferred embodiment, but it'is to be understood that I do not thereby intend to limit the invention to the specific form disclosed, but intend to coverall'mod'ifications and alternative 0on structions falling within the spirit and'scope ofthe invention as expressed in the appended claims.

Referring more particularly to the drawings, the motor constituting the embodiment of the invention comprises a suitable casing 10 which may be of any suitable form, and which in the present instance is generally cylindrical in shape to provide a generally cylindrical cam chamber 11. The casing 10 has front and

rear end walls

12 and 13 of which the front wall 12 has a removable cover plate l t-normally held in place by means of a plurality of bolts 15. Depending rom the body of the casing 10 and opening to the chamber 11 is a hollow base 16 which may be supported by any suitable means (not shown). In the present instance, suitable seats 17 which are adapted to receive and to be secured to parts of the support are pro- Vided in Opposite sides of the base 16. The casing 10 is suitably ribbed to provide strengdi and rigidity.

Opening in spaced relation to the cam chamber 11 are a plurality of suitable cylinders. Vdhile any desired plurality of cylinders may be provided, in the present instance I have shown sixequally spaced

cylinders

18, 19, 20, 21, 22 and 23 opening at their inner ends through the peripheral wall of the casing 10. Since these cylinders preferably are alike in construction, but one of them will be described, and corresponding parts of the others will be designated by like reference characters. Inthe preferred construction, each cylinder is formed separately of the casing 10, and has an outer air cooled end 2 and an inner end 25. The outer end 24 is closed by a suitable head 26 adapted to besecured thereto by means of bolts 27, and the inner end projects through an opening 28 in the peripheral wall of the casing. The cylinder is mounted in position by means of a peripheral flange 29 which is suitably secured to the peripheral margin of the opening 28 Formed in the head 26 are asuitable inlet valve 30 controlling a fuel inlet passage 31 adapted to be connected to a suitable fuel supply (not shown), and a suitable exhaust valve 32 controlling the outlet to the exhaust. The inner d the. cylinder is tapered in its outer surface at its inner'edge, as indicated at 33, to

' bring the inner ends of the cylinders closely together, and is formed in its front and rear sides with two diametrically opposed longitudinal slots 3e and 35, extending from the inner edge substantially to the peripheral wall of the casing 10.

Slidably disposed in the cylinders 18 to 23 respectively are a plurality of suitable pistons 37. 38. 39,40 and il. Preferably, the pistons are alike in construction, and hence but one of them will be specifically described, the corresponding partsv of the others however, being. designated by like reference characters. In the preferred construction, each piston is hollow, and the inner end thereofis formed with two diametrically opposed inwardly extending projections 42 having holesorbores43 in registration with the extending at its opposite ends through the 7

slots

34 and 35 is a pin 44. Two cam rollers sequence.

45 are suitably mounted on theends of the pin44 outside of the cylinder. In: the present instance, the ,camrollers 45 are mounted on ball bearings 46, and the latter are spaced from the piston by means of spacer sleeves 47 which are secured to the pin 44, and which bear againstthe sides of the slots'34gand 35 The parts, i. e., the piston, the pin 44, the

spacer sleeves 47 and the ball bearings 46 with the cam rollers 45 are held in assembled relation by means of suitable nuts 48 threaded onto the extreme ends of the pin.

The cam rollers 45 are arranged to coact with a suitable cam 49 for actuating the pistons in timed and uniform sequence. In the present instance, the cam 49 comprises two separate but identical plates 49a and 49b rotatably mounted in spaced and coincident relation at opposite sides of the cylinders 18 to 23 for engagement with the cam rollers45. By providing a' double cam and roller mechanism for actuating the pistons, a balanced central thrust is obtained and binding is avoided. Supporting the cam plates 49a and 49b is a suitable shaft 50 from which the power developed by the motor is adapted to be utilized. The shaft 50 is journalled in suitable ball bearings 51 and 52 secured respectively in bearing

sleeves

53 and 54 in the

end walls

12 and 13 of the casing 10. -The sleeve 54 is formed'on the end of a central hub 55 which projects outwardlyfrom the rear end wall 13 and which defines a small cylindrical chamber 56 opening to the chamber 11 sub stantially concentrically about the shaft 50. Preferably, the cam plates 49a and 495 are .formed with rearwardly extending

hubs

57 and 58 keyed to oppositely flared

portions

59 and 60 of the shaft 50, the hub 8 being disposed in the chamber 56.

Suitable packing glands

61 and 62 are secured inthe outer ends of the

sleeves

53 and 54 to close the latter and to seal the bearings for the shaft 50. V 7

If a motor comprises a single piston and cylinder unit, uniform operation can be ob-. tained by means of an actuatingcam having two spaced heads. If a motor comprises a plurality of piston and cylinder units uniformly spaced about the entire periphery of the casing, the same cam may be employed to operate the pistons in timed and uniform Obviously each piston will move through the four strokes of a complete cycle once for each complete revolution of the cam. A motor in which the pistonaud cylinder units are arranged in uniformly spaced rela-' tions about the entire periphery of the casing is impracticable for many purposes, such as farm use. The primary reasons for this are that the motor is bulky and cun1bersom-e,and

cannot be mounted satisfactorily, on land vehicles, partlcularly farm VQhIClGSL In; the

present invention,,I have therefore grouped the piston and cylinder units, in a portion of themotor casing, thereby saving in space, and proyidinga construction adaptable to a large variety of uses, including uses in stationary plants, and in landj andair vehicles.

-. Obviously, any desired number of piston andicylinder units may bezprovided, and these may be spaced over any desired portion of the casing, In the present instance, as recited in the foregomg, six piston and cylinder unlts areprovided, and thesepiston and. cylinder units are grouped-in uniformly spaced relation in the upper half of the casing 10'. The :end; piston and cylinder units are each inclined axially 15 from the horizontal, and

adj acentpiston and cylinder units are angularly'spaced 30?. Obviously, a cam having "but two spaced heads would not actuate the ,piston and cylinder: unitsin uniformly timed sequence sinceduring one half of one revolutlon each point on the cam, for example the firingTpoint or the exhaust point, would move idly throughspace. Hence, I have provided acam 49 having a plurality of peripherally spaced heads in a multiple of two correspondmg lnversely to that circumferential portion of'the casing in which the piston and cylinder units are'grouped. .In the present instance, the cam 49 is therefore provided with four

heads

63,64, and 66 which preferably are substantially uniformly peripherally spaced, and-of which the diametrically opposed heads 63 and .65 are conveniently designated as firing heads, and the diametrically

opposed heads

64 and 66 are conveniently designated as exhausting heads. It will be evident that as one head leaves the last piston and cylinder unit of the group, the opposite head comes into operative relation to the first piston and cylinder unit. 'I-Ience, the piston and cylinder unitsare actuated in uniformly timed sequence, and each piston goes through a complete cycle twice for each completerevolution of the cam 49. r p

Each of the cams [63 and 65has a curved face 67 for moving each piston out on the compression stroke, and a curved face 68 for controlling theinovement of the piston on the firing-stroke; Each of the

cams

64 and 66 has a curved face 69 for moving each piston out on the exhaust stroke,and a curved face 70 for controlling the inward movement of the piston-on the intake stroke. y

Preferably, the firing cams 63 and'65 are shorter than the cams 64 and 66so that a vari able stroke motor is obtained. As a result, the exhauststroke and the intake stroke are of maximum length sofas to completely exhaust the gases of combustion and to take in a 'freshcool .and undiluted charge of fuel. The advantages ofthis construction'are numerous: First, the deposition of carbon and detonations, which ordinarily occur through contact between the; fresh incoming fuel till - charge: and theunexpelled gases of combustion,-areavoided. -A-Inore dilu te fuel charge may'be' used, and "still complete and-'efiicient combustion will be obtained. -As a result, there will be no partially bur'ned gases 'and poisons such as carbon monoxide, to' be exhausted into the atmosphere. Since no inert gases with the temperature'of exhaust are presentatthe start of the intakestroke, undesirable high temperatures are avoided. The variable stroke-also kills vibration.

Preferably, the cam faces 67,- 68, '69 and 7O are so shaped that maximum efiiciencyisobtained in combustion and in'the mechanical development of the power generated. :In the present instance, the cam faces are so shaped that on the exhaust stroke the piston has a rapid preliminary movement and then a subsequent slow movement, on the inlet stroke the movement of the piston is initiated slowlyand is then accelerated to a speed greater than the maximum speed of the exhaust stroke, on the is obvious that the greatest leverage is obtained at the time when the most power is available.

To obtain continuity of propulsion, the firing faces 67 are of such length that the firing strokes of the pistons overlap, i; e., before the firing stroke of one, piston'is completed, the firing stroke of another piston is 'i-nitiated. As a result, dead centers are avoided. In the present instance, the

faces

68 and 70 extend on an arc of 35, and the faces 67 and'69 extend over an arc of 55. Since the 'piston and cylinderunits are spaced-"30 apart, the firing strokes for adjacent pistons and for'theen'd pistons will-overlap I Suitable means is provided for holding the cam-rollers45 'continua-lly'in contact with the cam 49. -Preferably.:this--means has a mechanical restoring action instead ofa spring action. A spring action is-not entirely satisfactory since it-may weaken and may-permit knocking. In the present instance, this means comprises a metallic restoring tape 71 (see Figs. 2 and'3) which engages a fixed retaining structure 7 2' and each of the pistons, and whichis suitably secured at its opposite ends. Preferably, the tape 71 extends'alternately over rollers 73 of which-oneis mounted in the inner end of each piston, and rollers 74 mounted inthe'structure 72. Seven rollers flt are provided,'andthese-are arranged in an are falling well within the inner most'noints'on the cam49. Successive rollers '73earerdisposd' in a line extending'substantially between successive pairs of the roll- 1 sis; 174. fEaclr=of: th-eirollers 73 is rotatably able. source of lubricant (not shown). "tube 81 opens to said rod 77, and extends rear walls of the oil casing 16. The upper ends of the standards 75 are arcuate in form and are disposed about the sleeve 57 of the cam plate 19a. The rollers 74 are suitably mounted on fixed bearing pins 79 secured between the upper ends of the standards 75.

Suitableoilingmeans is provided. 7 To thisv end, one of the hollow tubular rods 77 opens to a line'80 adapted to be connected to a suittherefrom upwardly and then about the sleeve 57 The upper curved end of the tube 81 is connected through a plurality of branch tubes 82 to the interior of the bearing pins 7 9. Each of the latter opens to admit oil -where desired.

The ends of the tape 71 are secured to tensioning'means in opposite sides of the casing 10 which preferably are alike in construction, and of which but one Will be described in detail, corresponding parts of the other however,being designated by like referencenumerals. Each tensioning means (see Figs. 3 and 6) comprises a hollow cylindrical casing 83 which is removably secured to one side'of the structure 72. and which is inclined upwardly and inwardly at approximately in a tangent line to the end roller 74:. The upper end of the casing 83 is partially closed by a. ring 84 through which the end of the tape 71 extends, and the lower end opens next to the side of the casing 10 in line with an opening closed by a plug 85 through which access to the tensioning means may be had. Slidably disposed in the casing 83 is a piston 86 carrying an axial stem 87 having av clamp head 88 in which the end of the tape is secured. In the present instance, the clamp head 88 is split longitudinally and has a lateral jaw-shaped opening in its free end. *The end of the tape is secured about a Wedge 89 in the opening, and the split portions of the head are clamped tightly against the tape by means of a nut 90 threaded onto the head. The head 88 is arranged eccentric-ally to the stem 87 so that the latter is in alignment with the outwardly extending tape. Disposed between the 84 and the piston'86 is a coiled spring 91. The tension of the spring 91 may be suitably adjusted by adjusting the stem'87 in the piston 86. It will be evident that the tensioning means serve to give the strip 71 any desired tension. In normal operation however,the ends of the tape are substantially statiohary,- since asone piston gives slack another one takes up slack to the same extent. As a result the'retaining means has primarily a mechanical action and not a spring action. By providing a retaining means of this character, the cam rollers 45 are retained securely and continually against the peripheral faces of the cam 49 throughout the complete cycle. As a result, the three pushes and the pull on the piston in the course of each cycle do not result in knocking, i. e., the pressure remains the same with reference to all. hearing parts. This makes it practicable to use ball bearings as described thereby obtaining a smooth even operation, and a low oil consumption consummation.

Means is provided for actuating the

valves

30 and 32 in timed relation to the reciprocation of the pistons. In the present instance, this means comprises a pair of

timingcams

92 and 93 mounted on the hub 58 of the cam plate 496' The cam 92 is adapted to coact with a plurality of radially reciprocatory plungers 94 sli dably disposed in bearing sleeves 95 formed inthe hub '55 and opening 1 to the periphery of the chamber 56. These plungers are connected respectively to aplurality of rods 96 which in turn are connected to suitable means 97 for actuating the valves 30. Similarly, the cam 93 is adapted to actuate a plurality of plungers 98 slidably disposed in sleeves 99, and connected through rods 100 to suitable means 101 for operating the valves 32. The rods 96 and 100 are suitably enclosed by hollow tubes 102 and the valve actuating mechanisms are suitably enclosed by casings 103, one on each cylinder head 26. The rods 96 and 100 extend in the same radial direction as their respective cylinders. The exhaust cam 92 has a pair of diametrically opposed lugs 104 which are adapted to be moved successively into successive engagement with the plungers 94, and

the intake cam 94 has a pair of diametrically opposed lugs 105 which are adapted to be moved into successive engagement with the plungers 98. It will be evident, that as one lug on either cam leaves the last plunger, the

other lug on said cam will engage the first .plunger. The cam 92 is positioned in ad- 'vance of the lnlet cam 93 so that each exhaust valve opens and closes just ahead of the companion inlet valve 32. r

Means is provided for supplying lubricant or oil to the casings 103 for the valve actuating mechanlsms. This means comprises an arcuate header 106 connected through-a plurality of branch feeder pipes 107 to the casings 103, and through a pipe 108 to one of ,the tubular rods 77, the other end of said rod being adapted to be connected to a suitable source of supply (not shown). Drip oil collecting in the bottom of the casing 16 may be withdrawn through a suitable opening 109. Because of the provision of a cam for actuating the piston and cylinder units, the

valve cams

92 and 93 can be drivendirectly with the cam, thereby eliminating timing gears and various other timing mechanism. As a result, an extremely simple, eflicient, fool-proof construction is obtained.

The operation will now be'briefiy described. Assuming that the cam 49 is rotating clockwise as appearing in Fig. 1, the piston 36 is near the end of its exhaust stroke, the piston 37 is at the start of its exhaust stroke, the piston 38 is on its firing stroke, the piston 39 is near the end of its compression stroke, the piston 40 is atthe start of its compression' stroke, and the piston 41 is at the start of its inlet stroke. As the cam 49 is rotated, each piston will be moved successively through an exhaust stroke, an inlet stroke, a compressionstroke and a firing stroke, and will go through two complete cycles for each revolution of the cam, Before the roller on the piston 38 leaves the cam surface 68, the roller on the piston 39 will move onto the cam surface, thereby insuring a continuity of propulsion. A short time'before the roller for the pfston 41 leaves thec am surface 68 of one of the heads 63 and 65, the roller for the piston 36 will engage the cam surface 67 of the other of the heads 63 and 65. Hence the piston and cylinder units will operate in uniformly timed sequence even though grouped in a portion of the'casing.

A variable stroke is obtained; The exhaust strokes are full, thereby completely expelling the burned gases, and hence insuring com plete and eflicient combustion of the incoming cha rge. Due to the mechanical restoring means which effectually retains the pistons in operative relation to the cam 49, no knocking results and hence'ball bearingscan be used to advantage. The construction is sim ple and compact, and by reason of the group ing of the piston and cylinder units in the upper portion of the casing, may be conven iently and securely mounted on a large variety of stationary and moving plants."

I claim as my invention: i I

1. In an internal combustion engine, in combination, a casing, a plurality of piston and cylinder units arranged in peripherally spaced relation and grouped in a portion of i the periphery of said casing, a shaft, an actu at-ing cam on said shaft,'said cam having plurality of peripherally spaced heads for moving each piston successively'in an intake stroke, a' compression stroke,-a firing stroke, and an exhaust stroke, said heads. being of" unequal length so that said intake stroke and" said exhaust stroke will be substantially longer than said compression stroke and said fir ingstroke, certain of said heads beingjsimilar so asto adapt them to periodically replace each other in operation so as to operate the pistons of said units continuously, retaining means for holding said pistons in operative relation to said cam,'means for adjusting said retaining.means,means for oiling said retaining means, inletand discharge valves'for said units, operating mechanisms for said valves, and a pair of timing cams rotatable with said actuating cam to actuate said valves in timed. relation to the movements of the pistons.

2. In an internal combustion engine, in combination, a casing, a plurality of piston and cylinder units grouped in a portion of said casing, a shaft, and an actuating cam on said shaft, said actuating cam having a plurality of peripherally spaced actuating heads, the number of heads being a multiple of a number which is the inverse of that circumferential portion of said casing occupied by said units, the pistons of said units being operatively related to said cam.

3. In a device of the class described, in combination, a plurality of piston and cylinder units, a'rotary cam, means on the pis-- tons engaging said cam, a stationary retaining structure, a mechanical retaining member extending alternately in engagement With said pistons and said retaining structure to hold said means against saidcam.

4. In a device of the class-described, in combination, a piston and cylinder unit, a rotary cam, a cam roller carried by the piston and engaging said .cam, a retaining structure mounted along-side said cam, said retaining structure having a pair of rollers, a roller-mounted in the inner end of said piston,-and a retaining tape fixed at its ends and extending over said rollers to hold said cam roller in contact with said cam.

5.111 a device Iof the class described, in combination, a casing, a piston and cylinder unit opening peripherally to said casing, a shaft, a cam on said shaft, said piston having .means operatively related to said cam, a retaining structure comprising a 'pair of vertically spaced standardsimounted in said casing, and encircling said shaft, a pair of rollers mounted between said standards and within the innermost circle of revolution of the cam face, .aroller mounted in the inner end of said piston, said piston roller being disposed substantially on a line between said rollers on said retaining structure, a retaining tape extending under said retaining rollers and over said piston roller, means for yieldingly securln g the-endsof said tape, and means 7 for adjusting the tension on'said tape.

tons in timed sequence without materially varying the tension in said member.

7. In a device of the class described, in combination, a casing, a piston and cylinder unit opening to said casing, a shaft, a double cam on said shaft, parts of said cam being disposed on opposite sides of said unit, said piston having a roller and having means operatively related to both parts of said cam, spaced retaining rollers mounted in said casing at opposite sides of said first mentioned roller and means for retaining said first mentioned means and said cam in operative relation, said last mentioned means extending under said retaining rollers and over said first mentioned roller, means for yieldingly securingthe ends of said tape, and means for tensioning said tape.

8. In a device of the class described, in combination, a plurality of piston and cylinder units, a rotary cam, means on the pistons engaging said cam, a stationary retaining structure, a retaining member extending alternately in engagement with said pistons and said retaining structure, and spring means yieldingly securing the ends of said member.

9. In a device of the class described, in combination, a casing, a piston and cylinder unit opening peripherally to said casing, a shaft, a cam on said shaft, said cam being double and disposed at opposite sides of said unit, said piston having means on opposite sides operatively related to said cam, a retaining structure comprising a pair of vertically spaced standards mounted between said cam parts .in said casing, and encircling said shaft, a pair of rollers mounted between said standards and within the innermost circle of revolution of thecam'face, a roller mounted in the inner end of said piston, a retaining member extending under said retaining rollers and over said piston roller, and means for yieldingly securing the ends of said member.

10. In a device of the class described, in combination, a retaining structure comprising a pair of standards, means for holding said standards in spaced relation, a plurality of rollers mounted between said standards, a flexible retaining member engaging said rollers and adapted to be flexed between said rollers, and adjustable means for tensioning said member.

In testimony whereof, I have hereunto affixed my signature.

ASA LEE RIGHTENOUR.