US3295748A

US3295748A - Arrangement for the continuous adjustment of the output of a piston compressor

Info

Publication number: US3295748A
Application number: US472455A
Authority: US
Inventors: Leitgeb Anton
Original assignee: Maschinenfabrik Burckhardt AG
Current assignee: Burckhardt Compression AG
Priority date: 1964-07-17
Filing date: 1965-07-16
Publication date: 1967-01-03
Anticipated expiration: 1984-01-03
Also published as: CH417835A; GB1092700A; DE1428005A1; NL6509166A

Description

Jan 3, W6? A. LEITGEB 339597413 ARRANGEMENT FOR THE CONTINUOUS ADJUSTMENT OF THE OUTPUT OF A PISTON COMPRESSOR Filed July 16, 1965 5 Sheets-Sheet 1 INVQENTOR mm mfiwb ATTORNEYS Jam. 3, W6? A. LEITGEB 393959748 ARRANGEMENT FOR THE CONTINUOUS ADJUSTMENT OF THE OUTPUT OF A PISTON COMPRESSOR Flled July 16, 1965 5 Sheets-$heet 2 INVENTUR mm Li MJMAQM ATTORN EYS Jan, 3,, 11%? A. LEiTGEB 3 ARRANGEMENT FOR THE CONTINUOUS ADJUSTMENT OF THE OUTPUT OF A PISTON COMPRESSOR Filed July 16, 1965 5 Sheets-Sheet 5 INVENTOR BY WMm ATTORNEYS United States Patent Ofiice 3,295,748- Patentecl Jan. 3, 1967 3,295,748 ARRANGEMENT FOR THE CONTINUOUS Al)- JUSTMENT OF THE OUTPUT OF A PISTON COMPRESSOR Anton Leitgeb, BaseL-Campagne, Switzerland, assignor to Maschinenfabrik Burckhardt AG., Basel, Switzerland, a corporation of Switzerland Filed July 16, 1965, Ser. No. 472,455 Claims priority, application Switzerland, July 17, 1964, 9,406/64 6 Claims. (Cl. 230--21) The present invention has for its object an arrangement adapted to adjust continuously the output of a pistoncontrolled compressor.

It is a well-known fact that it is possible to reduce the output of a piston compressor by connecting with the compression chamber an auxiliary compensating chamber. Said improved method allows obtaining a flattened shape for the return expansion and compression curves, whereby the sucked-in volume and the output delivered are reduced correspondingly. Such an arrangement operates theoretically without any loss, but the reduction in output is possible only stepwise.

It is also a well-known fact that it is possible to match the output in accordance with requirements and by resorting to a plurality of chambers of diffierent sizes, which allows obtaining an adjustment through a plurality of steps. Said improvement however requires considerable room for housing such auxiliary chambers which space is not always available.

It is also a wellknown fact that it is possible to ensure a continuous adjustment by restoring to an auxiliary chamber of a variable size. In such known arrangements, the auxiliary chamber is constituted by a cylinder inside which a piston is adapted to move so as to modify the volume of said chamber. The starting of the piston is however a diflicult matter, chiefly for high pressures, by reason of the high energy required for the movement of such a piston.

Lastly, an adjusting arrangement is also known for the auxiliary chamber, which ensures a continuous operation and wherein the auxiliary chamber is of an unvarying size, so as to allow a cutting out of the movable piston, said auxiliary chamber communicating with the cylinder during an adjustable duration. Said connection of a variable duration is ensured by a valve which may, under the action of a spring, be shifted during the compression stroke of the piston under the action of suitable means, so as to maintain the connection between the auxiliary chamber and the cylinder as long as the energy developed by the thrust of the gas acting on the closing member forming part of the valve is larger than the energy developed by the pressure of the spring. During the suction stroke of the piston, said valve is open as long as the pressure inside the cylinder is lower than the pressure of the spring so that consequently the gas enclosed in the auxiliary chamber returns into the cylinder, whereby the amount of gas sucked in is reduced correspondingly. With such an adjusting method, it is a difficult matter to ensure a long life for the movable parts, since it is not possible to prevent a considerable wear from being produced.

The present invention has for its object to cut out the above drawbacks by resorting to an arrangement for the continuous adjustment of the output, which arrangement includes an auxiliary chamber having a constant volume and which is filled with a fluid under a variable pressure.

According to said invention, this object is reached through the fact that the auxiliary chamber is connected with the compressor cylinder through a throttling member adapted to be locked and providing an adjustable crosssection for the flow of fluid, said throttling member being associated with a check and suction valve equipping the compressor cylinder; the arrangement thus devised is such that during the compression stroke of the piston, a fraction of the fluid to be compressed is delivered under pressure into the auxiliary chamber, which fraction returns during the suction stroke of the piston into the cylinder through the check valve and the throttling valve, whereby the volume of fluid sucked into the cylinder is reduced.

In such an arrangement, a predetermined pressure is established the value of which depends on the cross-section of the passageway provided by the throttling member into the auxiliary chamber and the value of said pressure may vary between Zero and the maximum value of the compression produced by the compressor. During the compression stroke and by reason of the pressure of the gas which is larger in the cylinder than in the auxiliary chamber, the check valve remains closed. In contradistinction, during the suction stroke, said valve opens when the pressure in the cylinder drops underneath that prevailing in the auxiliary chamber; the gas enclosed then escapes without being subjected to any throttling effect into the cylinder and this escape modifies correspondingly the volume of fluid sucked in in accordance with the amount of gas which has expanded.

The arrangement according to the invention as disclosed, operates without any loss under full load conditions when the throttling member is closed and the case is the same for the minimum output conditions to be considered when the throttling member is completely open, since no throttling is then performed. For adjustments ranging between these two extreme conditions, a slight loss through throttling appears. Such a loss is however very small since only a reduced fraction of the volume delivered is subjected to this throttling and furthermore the throttling is not performed between the output pressure and the suc tion pressure, but only down to the pressure prevailing at such a moment inside the auxiliary chamber. Such reduced losses are allowable since, on the other hand, the reliability in operation of the adjusting system is particularly high. The throttling member or valve includes a movable member, preferably a needle valve, which does not resonate with the machine so that it may operate freely and is not subjected to the action of disturbing members.

Further features and advantages of the invention will appear in the following description given by way of example reference being made to the accompanying diagrammatic drawings in which:

FIG. 1 is a transverse cross-section showing the auxiliary chamber equipping the head of the cylinder of a compressor. The whole system, the adjustable throttling member and the suction valve are fitted in the wall of said cylinder head, between the auxiliary chamber and the cylinder bore.

FIG. 2 is a transverse cross-section of a modified embodiment of the auxiliary chamber carrying a unit including the suction valve associated with the throttling member.

FIG. 3 is a cross-section of a further modification wherein the suction valve fitted in a central position forms a check valve or flap valve which opens towards the auxiliary chamber while its stroke is adjustable.

FIG. 4 is a transverse cross-section showing an arrangement according to which a fraction of the suction pipe serves as an auxiliary chamber as provided by the fitting of a second suction valve therein, said auxiliary chamber being connected with the cylinder bore through the agency of a throttling member lying outside the cylinder.

FIG. 5 is a cross-section of an arrangement similar to that illustrated in FIG. 4, wherein the throttling member connecting the cylinder bore with the auxiliary chamber is arranged centrally and inside the suction valve.

In all the figures of the accompanying drawings, 1 designates the auxiliary chamber which may be given any desired shape, while its volume corresponds to the maximum range required for adjustment; 2 designates the throttling member and 3 the check valve.

In the example illustrated in FIG. =1, the cross-sectional passage provided through the seat 4 of the throttling valve 2, which seat is fitted in the upper wall 17 of the cylinder 15, may be adjusted, as required by the pressure to be obtained in the auxiliary chamber 1, by the needle valve 5 controlled in an axial direction by a rod 6.

The shifting of the rod 6 is obtained by means of a hand-wheel 7 or the like control mechanism.

The adjustment of the cross-sectional area of the passageway opening towards the auxiliary chamber may as well be ensured by a cylindrical slide valve, instead of a needle valve. As illustrated in FIG. 1 for instance, the

. bottom of the auxiliary chamber may be provided in the usual manner, in the vicinity of the throttling member 2 with a check valve 3 forming also a suction valve opening into the bore of the compressor cylinder. The compressed gas entering the chamber 1 during the compression stroke of the piston 16 through the throttling member 2 expands inside the compressor cylinder during the subsequent suction stroke, the gas passing then without any loss due to throttling, through the passageway provided by the check valve 3 and the cross-sectional area uncovered by the throttling member. This ensures a variation in the amount of fluid sucked in in direct relationship with the adjusted pressure prevailing inside the auxiliary chamber 1 The embodiment illustrated in FIG. 2 differs from that illustrated in FIG. 1 through the fact that the seat 8 for the throttling member is formed centrally of the suction valve 3 which is given a generally annular shape. The cross-sectional area of the passageway open through the seat 8 is adjusted by the needle valve 5 forming the throttling member. Said coaxial arrangement of the unit including the suction valve and the throttling member is of advantage by reason of its reduced bulk, chiefly in the case of small diameter cylinders.

FIG. 3 illustrates an application of the invention according to which the suction valve 3 carried by the auxiliary chamber is associated with a throttling member forming also a check valve and located centrally of the suction valve 3. Said flap valve 9 opens towards the inside of the auxiliary chamber 1 and its stroke is limited by a stop 10 which may be shifted axially by suitable control means 11 so as to allow obtaining the desired adjusted throttling.

FIGS. 4 and 5 illustrate a modification of the arrangements according to FIGS. 1, 2 and 3, in which modification a fraction of the suction pipe 12 plays the part of an auxiliary chamber. In such a case, the auxiliary chamber is closed by a second suction valve 13 inserted ahead of the suction valve 3, the space lying between the two

valves

3 and 13 acting as the output adjusting means. The throttling member 2 which may be controlled by hand or through any other suitable means is shown as connected on the one hand with the bore in the cylinder 15 and on the other hand with the auxiliary chamber extending between the

valves

3 and 13. The operation is the same as that described with reference to the arrangements illustrated in FIGS. 1, 2 and 3.

Numerous modifications and additions may be brought to the above described adjusting system without widening the scope of the invention as defined in the accompanying claims; the embodiments described are in fact only exemplary and should by no means be construed in a limiting sense.

What I claim is:

1. In combination with a fluid compressor including at least one cylinder, a piston reciprocable therein, and at least one auxiliary pressure-adjusting chamber, the combination of two passages connecting said cylinder with the associated auxiliary chamber, an adjustable throttling member in one of said passages through which a fraction of the fluid compressed by the piston in the compressor cylinder is diverted into the auxiliary chamber, means adjusting the area of the passageway provided by the throttling member and a suction valve in the other passage allowing the passage of fluid from the auxiliary chamber into the compressor cylinder during the suction stroke of the piston in the compressor cylinder.

2. In combination with a fluid compressor including at least one cylinder, a piston reciprocable therein and at least one auxiliary pressure-adjusting chamber, the combination of two passages connecting said cylinder with the associated auxiliary chamber, an adjustable needle valve in One of said passages through which a fraction of the fluid compressed by the piston in the compressor or cylinder is diverted into the auxiliary chamber, means adjusting the area of the passageway provided by the needle valve and a suction valve in the other passage allowing the passage of fluid from the auxiliary chamber into the compressor cylinder during the suction stroke of the piston in the compressor cylinder.

3. In combination with a fluid compressor including at least one cylinder, a piston reciprocable therein, and at least one auxiliary pressure-adjusting chamber, separated by a partition from the cooperating cylinder, the combination of two passages extending through said partition and connecting said cylinder with the associated auxiliary chamber, an adjustable throttling member in one of said passages through which a fraction of the fluid compressed by the piston in the compressor or cylinder is diverted into the auxiliary chamber, means adjusting the area of the passageway provided by the throttling member and a suction valve in the other passage allowing the passage of fluid from the auxiliary chamber into the compressor cylinder during the suction stroke of the piston in the compressor cylinder.

4. In combination with a fluid compressor including at least one cylinder, a piston reciprocable therein and at least one auxiliary pressure-adjusting chamber, the combination of a first central passage and a second annular passage surrounding the first passage and connecting said cylinder with the associated auxiliary chamber, an adjustable throttling member in the first passage through which a fraction of the fluid compressed by the piston in the compressor or cylinder is diverted into the auxiliary chamber, means adjusting the area of the passageway provided by the throttling member and an annular suction valve in the second passage allowing the passage of fluid from the auxiliary chamber into the compressor cylinder during the suction stroke of the piston in the compressor cylinder.

5. In combination with a fluid compressor including at least one cylinder, a piston reciprocable therein and at least one auxiliary pressure-adjusting chamber, the combination of a suction pipe opening into the auxiliary chamber, a first suction valve between the suction pipe and the auxiliary chamber, two passages connecting said cylinder with the associated auxiliary chamber, an adjustalble throttling member in one of said passages through which a fraction of the fluid compressed by the piston in the compressor cylinder is diverted into the auxiliary chamber, means adjusting the area of the passageway provided by the throttling member and a second suction valve in the other passage allowing the passage of fluid from the auxiliary chamber back into the compressor cylinder during the suction stroke of the piston in the compressor cylinder.

6. In combination with a fluid compressor including at least one cylinder, a piston reciprocable therein and at least one auxiliary pressure-adjusting chamber, the combination of two passages connecting said cylinder with the associated auxiliary chamber, an adjustable throttling check valve in one of said passages through which a fraction of the fluid compressed by the piston in the compressor cylinder is diverted into the auxiliary chamber, an adjustable stop defining the outermost position to be assumed by the throttling check valve, means adjusting the location of said stop, and a suction valve in the other pas sage allowing the passage of fluid from the auxiliary chamher into the compressor cylinder during the suction stroke of the piston in the compressor cylinder.

References Cited by the Examiner UNITED STATES PATENTS 1,867,681 7/1932 Simpson 230-21 2,214,922 9/ 1940 Ericson 230-21 2,241,195 5/1941 Gehres 23021 DONLEY J. STOCKING, Primary Examiner.

W. J. KRAUSS, Assistant Examiner.