US3416453A - Diaphragm-type compressors and pumps - Google Patents

Description

' Dec. 17, 1968 FEUH-I-EBOls ETAL 3,416,453

DIAPHRAGM-TYPE COMPRES SORS AND PUMPS Filed March 8, 1967 2 Sheets-Sheet 1 [an/s [evil/chads 8ND Germain mat hand/rap; mzgida w L. FEUILLEBOIS ETAL- 3,416,453 I Dec. 17, 1968 DIAPHRAGM-TYPE COMPRESSOR S AND PUMPS 2 Sheets-Sheet 2 Filed March 8. 1967 1011/5 Q //eb0i$ 191/1 fer/"ail! 0/7210! United States Patent DIAPHRAGM-TYPE COMPRESSORS AND PUMPS Louis Feuillebois and Germain Ormut, Paris, France, as-

signors to Societe des Compresseurs a Membrane Corblin Filed Mar. 8, 1967, Ser. No. 621,558 Claims priority, application France, Mar. 24, 1966,

3 Claims. (Cl. 103-44 This invention is concerned with improvements in or relating to diaphragm-type pumps and compressors.

In apparatus of this character a generally metal diaphragm is positively oscillated in the biconcave space formed between a perforated plate and a head carrying the suction and delivery valves. The space left between the driving piston and the diaphragm is filled with an intermediate liquid. The apparatus is operated by the piston reciprocations transmitting a pulsatory motion of same frequency to said diaphragm.

The maximum volumetric efiiciency of the machine is obtained when the diaphragm engages completely the inner surface of the head at each piston stroke. As a rule this requirement is met by equipping the compressor with two ancillary devices as follows:

(1) A hydraulic fluid compensating pump, generally of the sliding piston type, driven through an eccentric keyed on the main crankshaft of the apparatus, this compensating pump delivering a certain quantity of hydraulic fluid into the main cylinder at each piston stroke; and

(2) A hydraulic pressure limiting device operating substantially like an overload valve and adjusted to open at a hydraulic pressure substantially higher than the gas pressure obtaining in the circuit fed by the compressor. Thus, the diaphragm contacts the head before the piston has attained its top dead centre position. Then, as the piston continues its stroke towards the top dead centre it compresses the hydraulic fluid, thus causing the pressure limiting device to open at each piston stroke.

It is a primary object of this invention to provide, in an apparatus of the type set hereinabove, an automatic hydraulic pressure limiting device which is both particularly efiicient and constructionally simple.

According to an essential feature of the present invention, this pressure limiting device comprises a valve member adapted to co-act with a seat and responsive on the one hand to the liquid pressure producing the diaphragm pulsations and on the other hand, through the medium of spring means, to a differential piston receiving on either faces the gas delivery pressure.

Besides, it may be noted that in the case of a gas compressor the gas pressure and the hydraulic fluid pressure vary as depicted in the diagrams of FIGURES 1a and 1b, plotting in abscisse the volumes displaced by the piston and in ordinates the pressure obtaining in the compression chamber.

When the compressor or pump delivers fluid at a constant pressure, the overpressure Ap, to which the diaphragm is subjected at the end of the piston stroke (FIG- URE la) is constant and in any case consistent with its 'ice mechanical strength. On the other hand, when the compressor or pump operates under variable delivery pressure conditions, notalbly when filling a reservoir with compressed \gas, the overpressure Ap applied to the diaphragm (FIGURE 1b) is subordinate to the gas delivery pressure, for a given setting of the pressure limiting device. Now the lower the gas delivery pressure, the higher this overpressure. Since the pressure limiting device must be set for a load corresponding to the maximum delivery pressure attained by the compressor, when this delivery pressure is low a very considerable pressure difference Ap is exerted against the diaphragm and is likely to be detrimental to its mechanical strength.

It is another object of this invention to avoid this inconvenience by providing the compressor or pump with an automatic hydraulic pressure limiting device adapted, irrespective of the conditions of operation of the machine, to maintain a constant ratio between the compressor delivery gas pressure and the hydraulic fluid pressure corresponding to the opening of the pressure limiting device.

In order to afford a clearer understanding of this invention and of the manner in which the same may be carried out in practice, reference will now be made to the accompanying drawings illustrating diagrammatically by way of example a typical form of embodiment of a hydraulic pressure limiting device according to this invention, which incorporates the improvements broadly set forth hereinalbove. In the drawings:

FIGURE 2 is a general axial sectional view of a diaphragm-type compressor incorporating an automatic hydraulic pressure limiting device according to this invention; and

FIGURE 3 is an axial detail view showing on a larger scale the automatic hydraulic pressure limiting device.

As shown in FIGURE 2, the compressor comprises in the known manner a head 10, a plate 11 and an intermediate perforated plate 12 formed with through holes 13, the head 10 and plates 11, 12 being assembled by means of bolts 14. A suitable gasket 15 is interposed between the intermediate perforated plate 12 and the lower plate 11.

A diaphragm or membrane 16 is clamped along its outer periphery between the head 10 and the intermediate plate 12, thus forming the variable-volume chamber '17 of the compressor. In the head 10 a delivery valve 18 and a suction valve 19 are mounted, as shown.

Coaxially to the lower plate 11 is a cylinder 20 having slidably mounted therein a piston 21 and leading into a chamber 22 formed between the intermediate plate 12 and the lower plate 11.

Journalled in a member 23 rigid with the lower end of piston 21 and slidalbly mounted in adequate guide means 24 is a gudgeon pin 25 connecting the piston 21 to the small end of a connecting rod 26 having its big end rotatably and drivingly mounted on a crankshaft 27. This crankshaft 27 is rotatably mounted in turn in a crankcase 28 by means of suitable bearings 29, 30 and driven by means of a grooved pulley 31. The rotation of this pulley 31, driven from a suitable motor (not shown), causes the reciprocation of piston 21 and the liquid fluid, for instance oil, contained in the cylinder 20 communicates to the diaphragm 16 a pulsatory motion having the same frequency as the piston reciprocations. The volumetric variations resulting from these pulsations in chamber 17 cause the fluid to be sucked from an inlet pipe 32 and delivered under pressure into pipe 33.

This apparatus further comprises a hydraulic fluid compensating pump 3-4 driven through an eccentric 35 keyed on the main crankshaft 27. This pump communicates on the one hand with the 'sump 36 of crankcase 28 and on the other hand with chamber 22 underneath the inter- 3 mediate plate 12 by means of a pipe line '37 comprising a non-return valve 38.

Finally, the apparatus comprises an automatic hydraulic pressure limiting device 40 constituting the subject-matter of the present invention.

In the form of embodiment illustrated in FIGURE 3 this automatic hydraulic pressure limiting device comprises a needle poppet 41 co-acting with a gaged seat 42 and controlling the outlet of a duct 43 communicating with the diaphragm actuating liquid at a pressure P This needle poppet 41 is movable in a chamber 44 communicating in turn through a port 45 with the sump 36 of the crankcase 28 of the compressor producing the liquid pressure.

Coaxially to the needle poppet 41 is a hydraulic servomotor consisting of a cylinder 46 having slidably mounted therein a differential piston 47 controlling said needle poppet 41 through the medium of a coil compression spring 48. The delivery pressure P of the gas compressed by the diaphragm 16 is transmitted through pipe line 39 and the branch lines 52 and 53 thereof to the two end faces of the differential piston 47, Le. its major face 49 and minor face 50. The piston movements are permitted by the provision of a vent hole 51 communicating with the external atmosphere.

During the operation of the device, the needle poppet 41 is subjected to the above-defined pressure P and the opposite faces 49 and 50 of differential piston 47 are subjected on the other hand to the gas pressure P The respective net surface areas S and S of the piston faces 49 and 50 are so calculated that the valve will open when the value of pressure P is such that the following equality is obtained:

wherein K is a predetermined factor greater than 1.

As the surface area S of face 49 is greater than the surface area S of face 50, the differential piston is responsive to a resultant force counteracting the valve unseating movement. The needle poppet 41 opens when the force applied thereto, which results from the hydraulic fluid pressure prevailing in cylinder 20, attains the force of opposite direction which is exerted on the diff rential piston.

The pressure limiting device illustrated in the drawing further comprises adjustable end stops 54 and 55 disposed at either end of the hydraulic servo-motor end adapted to be screwed in or out for setting their limit positions as desired.

The function of each adjustable end stop 54, 55 is explained hereinafter:

In the case of end stop 54, if for any reason the compressor or pump were subjected to a particularly high delivery pressure likely to impair the mechanical strength of the machine (for instance in case of accidental closing of the delivery valve of the machine), due to the automatic operation of the pressure limiting device a highly detrimental hydraulic overpressure may develop in cylinder 20. To avoid this drawback, the end stop 54 is so adjusted that when the gas delivery pressure P exceeds a limit value P the differential piston 47 will abut against the registering face 56 of this end stop 54. Under these conditions, the spring 48 is compressed with a force corresponding to a predetermined opening pressure of needle poppet 41. Under these conditions, the apparatus operates as a relief or safety valve.

In the case of the other end stop 55, if when the compressor is started no gas pressure is exerted against the differential piston 47 (for example when it is desired to fill up with gas an initially empty reservoir), the needle poppet 41 responsive to the pressure prevailing in cylinder 20 as a consequence of the upward stroke of piston 21 will be unseated and thus cause a hydraulic fluid flow before the diaphragm is urged upwards, so that the compressor will not operate. This inconvenience is avoided by the provision of the aforesaid end stop 55. This end stop is so adjusted that before the compressor is started the differential piston 47 receives a force urging the needle poppet 41 against its seat 42 through the medium of the coil compression spring 48.

Of course, this invention should not be construed as being limited by the specific form of embodiment illustrated and described herein, since various modifications and variations may be brought thereto without departing from the spirit and scope of the invention as set forth in the appended claims. Thus, notably, the differential piston 47 may comprise on its major face 49 a rod emerging from the outer face of end stop 55.

The applicability of the device is in any way limited to use with diaphragm-type compressors above described, but may be used with diaphragm-type compressors embodying somewhat different constructional features particularly as to method of assembling and sealing of head, method of drive and method of providing oil beneath the diaphragm.

What is claimed is:

1. In a diaphragm-type fluid compressor, comprising a diaphragm, two chambers separated by said diaphragm, a driving piston communicating with one of said chambers and the space between said driving piston and said diaphragm being filled with a liquid, suction and delivery valves in the other chamber, an automatic hydraulic pressure limiting device comprising a movable valve member, a seat engageable by said valve member, a pipe line connecting said seat to the compressor chamber containing the liquid acted upon by the compressor piston for pulsating the compressor diaphragm, and a differential piston adapted to move said valve member through the medium of a coil compression spring, said differential piston having its minor and major faces both connected to the gas delivery side of said compressor.

2. In a diaphragm-type fluid compressor, comprising a diaphragm, two chambers separated by said diaphragm, a driving piston communicating with one of said chambers and the space between said driving piston and said diaphragm being filled with a liquid, suction and delivery valves in the other chamber, an automatic hydraulic pressure limiting device comprising a movable needle poppet, a seat engageable by said needle poppet and a pipe line connecting said seat to the compressor chamber containing the liquid acted upon by the compressor piston for pulsating the compressor diaphragm, a differential piston adapted to move said needle poppet through the medium of a coil compression spring, means for simultaneously connecting the minor and major faces of said differential piston to the gas delivery side of said corn pressor, and adjustable end stop adapted to be engaged by said differential piston when the gas delivery pressure attains a predetermined value, whereby said differential piston can transmit to said needle poppet a compressive effort corresponding to a predetermined valve opening pressure and said pressure limiting device can operate as a safety valve.

3. In a diaphragm-type fluid compressor, comprising a diaphragm, two chambers separated by said diaphragm, a driving piston communicating with one of said chambers and the space between said driving piston and said diaphragm being filled with a liquid, suction and delivery valves in the other chamber, an automatic hydraulic pressure limiting device comprising a movable needle poppet, a seat engageable by said needle poppet and a pipe line connetcing said seat to the compressor chamber containing the liquid acted upon by the compressor piston for pulsating the compressor diaphragm a differential piston adapted to move said needle poppet through the medium of a coil compression spring, means for simultaneously connecting the minor and major faces of said differential piston to the gas delivery side of said compressor, a first adjustable end stop adapted to be engaged by one end of said differential piston when the gas delivery pressure attains a predetermined value whereby said differential piston can transmit to said needle poppet a compressive effort corresponding to a predetermined value opening pressure and said pressure limiting device can operate as a safety valve, a second adjustable end stop adapted to be engaged by the oppo- 5 6 References Cited UNITED STATES PATENTS 1,651,964 12/ 1927 Nelson 230-44 2,753,805 7/ 1956 Boivinet 10344 2,971,465 2/1961 Caillaud 103-44 ROBERT M. WALKER, Primary Examiner.

Images