Patent Application
20120118141
The present invention relates to a plunger-type measuring pump for measuring out and sending an amount of liquid by driving a plunger into a reciprocating motion
Plunger-type measuring pumps are widely used as a mechanism for measuring out an amount of liquid and sending it to an analytical instrument or other systems. A plunger-type measuring pump is a device in which a plunger is reciprocated in a pump chamber to continuously feed a constant amount of liquid.
When the plunger 2 is reciprocated in the pump chamber 31, a specified constant amount of liquid is sucked through the suction port 32 into the pump chamber 31 and sent to an analytical instrument or other systems.
Patent Document 1: JP-A 10-103221
In this conventional plunger-type measuring pump, the pump head 3 is attached to the pump body 1 with a plurality of fixing parts 6, such as bolts. If these bolts are unevenly tightened, the pump head 3 attached to the pump body 1 will be inclined, causing an uneven force on the plunger seal 4, which results in a deformation of the plunger seal 4. The deformation of the plunger seal 4 leads to the leakage of liquid from the pump chamber 31, the breakage of the plunger seal 4 and the shortening of its life.
The aforementioned problems can be avoided by evenly tightening the bolts 6. However, it requires a skilled technician to meticulously tighten the bolts 6. Thus, a considerable amount of time and labor is needed to attach the pump head 3.
The present invention has been developed in view of the aforementioned problem, and its objective is to reduce the time and labor for correctly attaching the pump head to the pump body.
In a plunger-type measuring pump for sending liquid by reciprocating a plunger in a pump chamber, the plunger-type measuring pump according to the present invention is characterized by including:
a pump body for supporting the plunger while allowing a reciprocating motion of the plunger;
a cylindrical head-attachment portion provided at one end of the pump body, the head-attachment portion having a male-thread portion on an outer circumference thereof;
a pump head having the pump chamber inside, the pump head being designed to be attached to the head-attachment portion with a seal therebetween; and
a sleeve-like fixing part to be fitted onto the outer circumference of the pump head, the sleeve-like fixing part having an inner circumferential wall on which an engaging portion to be engaged with the pump head and a female-thread portion to be screwed onto the male-thread portion are formed.
In one mode of the aforementioned plunger-type measuring pump, the pump head has a flange with which the engaging portion is to be engaged.
In another mode of the aforementioned plunger-type measuring pump, the sleeve-like fixing part has a large-hole section having a large inner diameter and a small-hole section having a small inner diameter, and the engaging portion is a boundary section between the large-hole section and the small-hole section.
In the plunger-type measuring pump according to the present invention, a single sleeve-like fixing part is used to fix the pump head to the cylindrical head-attachment portion provided on the pump body. Unlike the conventional case where a plurality of bolts are used to fix the pump head, it is unnecessary to pay attention to the evenness of the tightening force.
The pump head is attached to the pump body by screwing the female thread formed on the inner circumferential surface of the sleeve-like fixing part on the male thread formed on the outer circumferential surface of the head-attachment portion. Accordingly, there is no need to use any tool in the attaching work, and the pump head can be correctly attached with a small amount of time and labor.
One embodiment of the present invention is hereinafter described by means of
A major difference between the plunger-type measuring pump of the present embodiment and the conventional example exists in that the present pump uses a single fixing part 7 to fix the pump head 9 to the pump body 1.
More specifically, a projection 8 is integrally formed at one end of the pomp body 1. The projection 8 has a cylindrical section 81 and a large-diameter section 82 whose outer diameter is larger than that of the cylindrical section 81. The large-diameter section 82 is provided at the anterior end of the cylindrical section 81. A male-thread groove 83 is formed on the outer circumference of the large-diameter section 82. A depression for receiving a cylindrical seal holder 5 is formed on the side of the projection 8 facing the pump head 9. The plunger 2 is supported by the pomp body 1 in such a manner that it can reciprocate. The tip of the plunger 2 protrudes from the projection 8.
The pump head 9 has a cylindrical body having a flange 94 at one end. The outer diameter of this flange 94 is approximately equal to that of the large-diameter section 82 of the cylindrical section 8. A depression for receiving the seal holder 5 and a pump chamber 91 are formed inside the pump head 9. Furthermore, the pump head 9 has a liquid suction port 92 for sucking liquid into the pump chamber 91 and a liquid discharge port 93 for discharging liquid from the pump chamber 91.
The seal holder 5 is a cylindrical part having a through hole 51 extending in the axial direction, with a seal 4 being held on the side of the seal holder 5 facing the pump head 9. The seal 4 has a convex shape with the projecting side facing the pump body 1.
The fixing part 7 has a nut-like shape with a through hole at its center. This through hole is divided into a large-hole section 71 having a large inner diameter and a small-hole section 73 having a small inner diameter. The inner diameter of the large-hole section 71 is slightly larger than the outer diameter of the large-diameter section 82. A female-thread groove 72, which is designed to be screwed onto the aforementioned male-thread groove 83, is formed on the inner circumferential wall of the large-hole section 71. The thickness of the large-hole section 71 at a portion where no female-thread groove 72 is formed is slightly larger than that of the flange 94 of the pump head 9. The inner diameter of the small-hole section 73 is slightly larger than the outer diameter of the pump head 9.
To facilitate the tightening of the fixing part 7, four flat faces are formed on the outer circumference of the fixing part 7. The fixing part 7 is made of resin and produced as a single-piece part.
In the measuring pump 10 of the present embodiment, the pump head 9 is attached to the pump body 1 as follows: Initially, the seal holder 5 is fitted into the depression of the projection 8 of the pump body 1, with the tip of the plunger 2 being inserted into the through hole 51 of the seal holder 5. Next, the pump head 9 is attached. More specifically, the plunger 2 protruding from the seal holder 5 is fitted into the pump chamber 91 of the pump head 9 and the seal holder 5 is fitted into the depression of the pump head 9 so that the flange 94 comes in contact with the end face of the large-diameter section 82.
Subsequently, the fixing part 7 is put on the pump head 9 from the anterior side and screwed to make the female-thread groove 72 engaged with the male-thread groove 83 of the large-diameter section 82. In this process, the step-like portion at the boundary of the large-hole section 71 and the small-hole section 73 (this portion is hereinafter called the “step section 74”) comes in contact with the flange 94 of the pump head 9. The fixing part 7 is strongly tightened until the flange 94 is pressed on the large-diameter section 82. As a result, the pump head is strongly fixed to the projection.
In this manner, the pump head 9 is attached to the pump body 1 with a single fixing part 7. Accordingly, it is possible to correctly attach the pump head 9 to the pump body 1 even without taking account of the balance of the tightening force of the fixing part. The force acting on the plunger seal 4 also becomes uniform, so that no deformation of the plunger seal 4 will occur.
The tightening of the fixing part 7 requires no expert skills or special tools. Therefore, the pump head 9 can be easily attached by hand work. Thus, the amount of time and labor for the attaching work is reduced.
Such an effect is particularly profitable when the plunger 2 has a large diameter (e.g. 6 mm or greater). Increasing the diameter of the plunger 2 requires a corresponding increase in the size of the plunger seal 4 and the pump head 9, causing the effect of an inclination of the pump head 9 to be more noticeable and the deformation of the plunger seal 4 to be more likely to occur.
The fixing part 7 can be used to fix the pump head 9 to the projection 8 even if the flange 94 is thinner than the portion of the large-hole section 71 where no female thread 72 is formed. Even in this case, the pump head 9 can be fixed to the projection 8 since the fixing part 7 can be screwed until the step section 74 comes in contact with the flange 94 (see
The fixing part 7 is also applicable to a pump head 9 having a flange 94 whose outer diameter is smaller than that of the large-diameter section 82. Even in this case, the pump head 9 can be fixed to the projection 8 since the fixing part 7 can be screwed until a portion of the step portion 74 comes in contact with the flange 94 (see
Thus, according to the present invention, a fixing part 7 of the same size can be commonly used even if the dimensions of the flange are slightly different.
Thus far, one mode for carrying out the present invention has been described by means of the embodiment and variations. It should be noted that the present invention is not limited to the previous examples; they can be appropriately changed within the spirit of the present invention. For example, the projection 8 of the pump body 1 may have the same external dimensions at every portion. The pump head 9 does not need to be cylindrical in its entirety; the minimal requirement is that the portion of the pump head 9 to be fixed with the fixing part 7 (i.e. the portion facing the pump body 1) is cylindrical. In this case, the anterior portion of the pump head 9 must have an appropriate size so that the fixing part 7 can be fitted on that portion.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2009/003526 | 7/27/2009 | WO | 00 | 1/27/2012 |
