Two-stage pump assembly

• US 4,681,513 A
• Filed: 01/28/1986
• Issued: 07/21/1987
• Est. Priority Date: 02/01/1985
• Status: Expired due to Term

• Current Assignee: JEOL Limited
• Original Assignee: JEOL Limited
• Inventors: Takeuchi, Makoto, Saito, Toshinori
• Primary Examiner(s): Croyle, Carlton R.
• Assistant Examiner(s): NOT, DEFINED
• Application Number:
  US06/823,341
• Time in Patent Office: 539 Days
• Field of Search: 417/2, 417/18, 417/45, 417/53, 417/63, 417/265
• US Class Current: 417/2
• CPC Class Codes: F04B 1/02 having two cylinders in V-arrangement F04B1/04
• CPC Class Codes: F04B 49/06 Control using electricity regulating by means of floats actuating electric switches F04B49/04
• CPC Class Codes: G01N 2030/324 speed, flow rate
• CPC Class Codes: G01N 2030/326 pumps
• CPC Class Codes: G01N 30/36 in high pressure liquid systems

Abstract

An accurately controllable two-stage pump assembly comprising two plunger pumps connected in series. The suction port of the outlet pump A is connected to the discharge port of the inlet pump B, so that the discharge port of the outlet pump A and the suction port of the inlet pump B act as the discharge port and the suction port, respectively, of the whole pump assembly. While the inlet pump B is delivering fluid from the whole pump assembly, the outlet pump A completes the filling stroke of the whole pump assembly and fully increases the pressure inside the chamber of the outlet pump A. While the inlet pump B is filling, the outlet pump A is in the stage of displacement stroke and delivers fluid from the whole pump assembly. The plungers of the pumps are moved via cams by stepper motors which swing or rotate back and forth within a certain angular range.

Claims

1. In a two-stage pump assembly having two pumps A and B and a control means for controlling the operation of each pump in such a way that the pump assembly delivers fluid, each of the two pumps having a cylinder constituting a chamber, a plunger fitted in the cylinder and making reciprocating motion to vary the capacity of the chamber, and one-way valves disposed at the suction port and at the discharge port, respectively, of the chamber, the improvement comprising:

(A) the suction port of the pump A is connected to the discharge port of the pump B, and the discharge port of the pump A and the suction port of the pump B act as the discharge port and the suction port, respectively, of the whole pump assembly;

(B) said means for controlling causing the suction stroke of the pump B (period T_b1) to start simultaneously with the discharge stroke of the pump A (period T_a1), and the discharge of the pump B (period T_b3) to start simultaneously with the suction stroke of the pump A (period T_a3);

(C) said means for controlling causing a compression stroke in pump B during a period of T_b2 between the suction stroke and the discharge of the pump B;

(D) the periods being so set as to satisfy the following reactions;

space="preserve" listing-type="equation">I.sub.a1 =T.sub.b1 +T.sub.b2, T.sub.a3 =T.sub.b3, T.sub.a1 >

T.sub.a3, T.sub.b1 >

T.sub.a3 ;

and,

(E) wherein said means for controlling each pump comprises

(i) two stepper motors each having a rotating output shaft and the capability of causing rotation of the shaft in either direction,

(ii) cams fixed to each rotating shaft for bearing upon followers attached to the exposed ends of each plunger respectively, and

(iii) said stepper motors being controlled to rotate back and forth within an angular range controlled according to the desired flow rate.

5. In a two-stage pump assembly as set forth in claims 1, 2 or 3, the further improvement wherein the profile of each cam is so made that the distance traveled by each plunger whenever the corresponding stepper motor rotates a unit step angle varies among different angular ranges.

2. In a two-stage pump assembly having two pumps A and B and a control means for controlling the opration of each pump in such a way that the pump assembly delivers fluid, each of the two pumps having a cylinder constituting a chamber, a plunger fitted in the cylinder and making reciprocating motion to vary the capacity of the chamber, and one-way valves disposed at the suction port and at the discharge port, respectively, of the chamber, the improvement comprising:

(A) the suction port of the pump A is connected to the discharge port of the pump B, and the discharge port of the pump A and the suction port of the pump B act as the discharge port and the suction port, respectively, of the whole pump assembly;

(B) said means for controlling causing the suction stroke of the pump B (period T_b1) to start simultaneously with the discharge stroke of the pump A (period T_a1), and the discharge of the pump B (period T_b3) to start simultaneously with the suction stroke of the pump A (period T_a3);

(C) said means for controlling causing a compression stroke in pump B during a period of T_b2 between the suction stroke and the discharge of the pump B;

(D) the periods being so set as to satisfy the following relations;

space="preserve" listing-type="equation">T.sub.a1 =T.sub.b1 +T.sub.b2, T.sub.a3 =T.sub.b3, T.sub.a1 >

T.sub.a3, T.sub.b1 >

T.sub.a3

(E) there being provided means for detecting variations in the pressure at the discharge port of the pump A and for displaying the resultant signal in synchronism with the operation of the pump A; and

,

(F) wherein said means for controlling each pump comprises

(i) two stepper motors each having a rotating output shaft and the capability of causing rotation of the shaft in either direction,

(ii) cams fixed to each rotating shaft for bearing upon followers attached to the exposed ends of each plunger respectively, and

(iii) said stepper motors being controlled to rotate back and forth within an angular range controlled according to the desired flow rate.

3. In a two-stage pump assembly having two pumps A and B and a control means for controlling the operation of each pump in such a way that the pump assembly delivers fluid, each of the two pumps having a cylinder constituting a chamber, a plunger fitted in the cylinder and making reciprocating motion to vary the capacity of the chamber, and one-way valves disposed at the suction port and at the discharge port, respectively, of the chamber, the improvement comprising:

(A) the suction port of the pump A is connected to the discharge port of the pump B, and the discharge port of the pump A and the suction port of the pump B act as the discharge port and the suction port, respectively, of the whole pump assembly;

(B) said means for controlling causing the suction stroke of the pump B (period T_b1) to start simultaneously with the discharge stroke of the pump A (period T_a1), and the discharge of the pump B (period T_b3) to start simultaneously with the suction stroke of the pump A (period T_a3);

(C) said means for controlling causing a compression stroke in pump B during a period of T_b2 between the suction stroke and the discharge of the pump B;

(D) the periods being so set as to satisfy the following relations;

space="preserve" listing-type="equation">T.sub.a1 =T.sub.b1 +T.sub.b2, T.sub.a3 =T.sub.b3, T.sub.a1 >

T.sub.a3, T.sub.b1 >

T.sub.a3

(E) means for detecting the variation in the pressure at the discharge port of the pump A that occurs during each stroke and for controlling the angular velocity of a stepper motor driving the plunger of the pump B during the periods T_b1 and T_b2 whereby variations in the pressure at the discharge port of the pump A are reduced; and

,

(F) wherein said means for controlling each pump comprises

(i) two stepper motors each having a rotating output shaft and the capability of causing rotation of the shaft in either direction,

(ii) cams fixed to each rotating shaft for bearing upon followers attached to the exposed ends of each plunger respectively, and

(iii) said stepper motors being controlled to rotate back and forth within an angular range controlled according to the desired flow rate.

4. In a two-stage pump assembly as set forth in claim 3, the further improvement comprising means for detecting a signal indicative of the position of the plunger in pump A and means for controlling the angular velocity of the stepper motor driving the plunger of pump B in response to the pressure variation signal and the position signal.