Injecting machine for injecting mixture of two different liquids in first-in and first-out manner

An injecting machine includes an injection cylinder, a plunger, a plunger moving mechanism, and a mixing mechanism. The plunger is reciprocally received in the injection cylinder for moving between an advanced position and a retracted position, with the injecting a liquid mixture of two different liquid materials as the plunger moves to the advanced position. The plunger moving mechanism causes the plunger to move between the advanced position and the retracted position. The mixing mechanism is disposed on the injection cylinder for mixing the two different liquid materials together to feed the liquid mixture into the injection cylinder. The plunger includes a front portion having a helical groove formed on an outer circumferential surface thereof to allow the liquid mixture fed from the mixing mechanism to pass through the helical groove for collecting in a forward space formed forward of the front portion of the plunger.

FIELD OF THE INVENTION

The present invention relates to an improvement in an injecting machine for two different liquids.

BACKGROUND OF THE INVENTION

An injecting machine for receiving and mixing two different liquids together to inject a predetermined measured amount of a mixture of the two different liquids is known as disclosed in JP-A-2007-76276.

FIG. 8hereof shows an injecting machine disclosed in JP-A-2007-76276. A first cylinder101forces a first liquid102out while a second cylinder103forces a second liquid104out. The first liquid102and the second liquid104are combined together in a mixer105to flow into a mixing cylinder106. The first and second liquids102,104are sufficiently mixed together by rotation of a mixing shaft107in the mixing cylinder106to provide a liquid mixture of the first and second liquids102,104. The liquid mixture is introduced through a connecting passage into an injection cylinder109.

Referring toFIG. 9A, the liquid mixture indicated at111collects in a forward space formed forwardly of a plunger112. The forward space becomes large as the plunger112moves back, thereby increasing an amount of the collecting liquid mixture. As shown inFIG. 9B, a sufficient amount of the liquid mixture collects in the forward space immediately before injection of the liquid mixture when the plunger112is in a sufficiently retracted position.

The liquid mixture111collects in the forward space as follows. A first part111aof the mixture first enters the forward space and then moves back with the plunger112such that the succeeding part of the mixture enters the forward space, and a last part111bof the mixture finally enters and remains in the forward space furthest from the plunger112.

As the plunger112advances, the mixture is injected in a “first-in last-out” manner in which the last part111bwhich finally entered the forward space is first injected and the first part111awhich first entered the forward space is finally injected.

The liquid material tends to change its quality as time elapses. The first part111aremains in the forward space for a long time while the last part111bremains in the forward space for a short time. Since the first part111aand the last part111bremain in the forward space for different periods of time, as a result, undesirable difference in quality between the first part111aand the last part111boccurs. As measures against this undesirable quality difference, it is necessary for an injecting machine to inject a liquid mixture in a “first-in first-out” manner.

An object of the present invention is to provide an injecting machine for two different liquids, the machine being configured to inject a mixture of the two different liquids in a first-in first-out manner.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, there is provided an injecting machine for two different liquid materials, comprising: an injection cylinder having a nozzle disposed on a distal end thereof; a plunger reciprocally received in the injection cylinder for moving between an advanced position and a retracted position, the plunger injecting a liquid mixture of the two different liquid materials as the plunger moves to the advanced position; plunger moving means for causing the plunger to move between the advanced position and the retracted position; and a mixing mechanism disposed on the injection cylinder for mixing the two different liquid materials together to feed the liquid mixture into the injection cylinder, and wherein the plunger includes a front portion having a helical groove formed on an outer circumferential surface thereof to allow the liquid mixture fed from the mixing mechanism to pass through the helical groove for collecting in a forward space formed forward of the front portion of the plunger.

The liquid mixture is directed by the helical groove of the plunger into the forward space formed forwardly of the plunger, in such a manner that a first part of the mixture first enters and remains in a front portion of the forward space and a last part of the mixture finally enters and remains in a rear portion of the forward space closest to the plunger. Movement of the plunger to the advanced position first injects the first part of the mixture. That is, the liquid mixture is injected in the first-in first-out manner to thereby prevent occurrence of difference in quality between the first part and the last part.

In a preferred form of the present invention, the two different liquid materials include a first liquid material and a second liquid material, and the mixing mechanism comprises: a mixing block; a screw rotatably accommodated in the mixing block; a screw rotating mechanism supported on the mixing block for rotating the screw; a first liquid supply passage disposed at a first portion of the mixing block for supplying the first liquid material to a proximal portion of the screw; a second liquid supply passage disposed at a second portion of the mixing block for supplying the second liquid material to the proximal portion of the screw, the second portion being separate from the first portion; and a first passage formed in the mixing block for causing the liquid mixture to flow out of a vicinity of a distal end of the screw.

An appropriate control over a rotational speed of the screw ensures a sufficient mixing time to help mix the first liquid material and the second liquid material together. Rotation of the screw feeds the first and second liquid materials at a low pressure.

In a further preferred form of the present invention, the first liquid supply passage has a first connection port formed in the first portion of the mixing block, and the second liquid supply passage has a second connection port formed in the second portion of the mixing block, the first connection port and the second connection port being arranged on a line passing through an axis of rotation of the screw, and the screw is interposed between the first connection port of the first liquid supply passage and the second connection port of the second liquid supply passage.

The first and second connection ports of the first and second liquid supply passages are formed together just by making a single hole through the mixing block. This results in the machining cost of the mixing block being reduced.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As shown inFIG. 1, an injecting machine10for two different liquids includes an injection cylinder12having a nozzle11disposed on a distal end thereof, a bar-shaped plunger13axially movably received in the injection cylinder12, a support plate14supporting a proximal portion of the injection cylinder12, and a base15supporting the support plate14. The machine10further includes a cylinder support plate16attached to the base15and disposed in parallel to the support plate14. The machine10also includes plunger moving means17supported on the cylinder support plate16for reciprocating the plunger13between an advanced position and a retracted position. The machine10also includes a mixing mechanism20attached to a top surface of the injection cylinder12.

The plunger13has a helical groove13aformed on a front portion thereof.

The support plate14and the cylinder support plate16have their upper portions connected together by means of a tie rod18to prevent sway of the support plate14and the cylinder support plate16.

The plunger moving means17is preferably a hydraulic cylinder, an air cylinder or an electric cylinder.

As shown inFIG. 2, the mixing mechanism20includes a body21carried on the top surface of the injection cylinder12, a valve member22vertically movably received in the body21, and a valve actuator24secured to a top of the body21through bolts23,23for moving the valve member22vertically. The mixing mechanism20further includes a mixing block25attached to a lateral side of the body21, a screw26rotatably received in the mixing block25, and a screw rotating mechanism27attached to one end of the mixing block25for rotating the screw26.

The screw rotating mechanism27is preferably an electric motor having a speed reducer.

A horizontal first passage28is formed in the mixing block25and extends into the body21. A second passage29extends vertically downwardly from a distal end of the first passage28out of the body21and into the injection cylinder12. When driven by the valve actuator24to move downwardly to a closed position, the valve member22closes the second passage29. When driven by the valve actuator24to move upwardly to an open position, the valve member22brings the second passage29into fluid communication with the first passage28.

As shown inFIG. 3, the screw26includes a helical blade26aand is accommodated in a mixing chamber31formed within the mixing block25. The mixing chamber31has a lower portion communicating with the first passage28. The mixing chamber31has an upper portion communicating with first and second liquid supply passages32,33. The first liquid supply passage32is adapted to deliver a first liquid or first liquid material35, which has been forced out of a first cylinder34, to the mixing chamber31. The second liquid supply passage33is adapted to deliver a second liquid or second liquid material37, which has been forced out of a second cylinder36, to the mixing chamber31. The first liquid supply passage32has a first connection port32acommunicating with the upper portion of the mixing chamber31, and the second liquid supply passage33has a second connection port33acommunicating with the upper portion of the mixing chamber31. These connection ports32a,33acan be formed by performing a drilling operation once on the mixing block25.

As shown inFIG. 4, the first connection port32aof the first liquid supply passage32and the second connection port33aof the second liquid supply passage33are arranged on a line38passing through an axis of rotation of the screw26, and the screw26is interposed between the first connection port32aand the second connection port33a.

InFIG. 3, the screw rotating mechanism27rotates the screw26at a low speed, preferably, in a reverse direction as shown by an arrow (1). During the rotation of the screw26, the first liquid35is delivered from the first liquid supply passage32into the mixing chamber31while the second liquid37is delivered from the second liquid supply passage33into the mixing chamber31.

Since the screw26is positioned centrally of the mixing block25, as shown inFIG. 4, the first and second liquids35,37each first hit a proximal portion of the screw without mixing together. Thereafter, the first and second liquids35,37each advance or flow down in a helical line along the helical blade26a. A speed of the advancement (downward flow) of each of the first and second liquids35,37is reduced due to the low speed reverse rotation of the screw as shown by the arrow (1). That is, the first and second liquids35,37are agitated and mixed together by the screw26over a long period of time. The reverse rotation of the screw26sufficiently mixes the first and second liquids35,37together even where the screw26is short.

A liquid mixture39of the first and second liquids35,37passes from the second passage29through the helical groove13ato collect in a forward space formed forwardly of the front portion of the plunger13, as shown inFIG. 5A, as the plunger13gradually moves back.

The first liquid35is, for example, a curing agent (liquid silicone rubber) and the second liquid37is, for example, a base agent (liquid silicone rubber). After the second liquid37is mixed into the first liquid35, the mixture of the first and second liquids35,37changes in (physical) quality as time elapses.

When the plunger moves back to a fully retracted position, as shown inFIG. 5B, a first part39sof the mixture39, which has first entered the forward space formed forwardly of the front portion of the plunger13, remains in a front portion of the forward space while a last part39eof the mixture39, which has finally entered the forward space, remains in a rear portion of the forward space (the rear portion being closest to the front portion of the plunger13). As the plunger moves toward the advanced position, the first part39sof the mixture39is first injected out of the nozzle11, and the last part39eof the mixture39is finally injected out of the nozzle11. That is, the mixture39is injected in a “first-in first-out” manner such that a period of time during which the first part39sremains in the injection cylinder12approximates a period of time during which the last part39eremains in the injection cylinder12to thereby prevent occurrence of difference in quality between the first part39sand the last part39e. As a result, it becomes possible to reduce a maintenance time to prevent hardening of the mixture in the production process. In addition, it becomes possible to run the machine10continuously for an increased period of time so as to improve the productivity.

Referring back toFIG. 2, the first passage extends perpendicularly to the plunger13, and the mixing block25, the screw26and the screw rotating mechanism27are spaced a distance L away from the plunger13. As a result, a moment directed in a counterclockwise direction in this figure is produced about the plunger13. This moment acts as a twisting force on the injection cylinder12. Where the mixing block25, the screw26and the screw rotating mechanism27are made large in size, the moment increases and affects the injection cylinder12.

It is preferable that no moment is produced in the machine. Discussion is made below as to an injecting machine modified to produce no moment discussed above.

As shown inFIG. 6, the first passage28extends in parallel to the plunger13. That is, the body21and the mixing block25are arranged in a direction along an axis of the injection cylinder12. This arrangement eliminates concern over generation of a moment which acts on the injection cylinder12. Other elements of the modified injecting machine shown inFIG. 6are the same as those of the injecting machine10and hence their discussions are omitted.

Discussion is made below as to a further modification to the injecting machine.

As shown inFIG. 7, the mixing mechanism20may include a static mixer41. The static mixer41includes the mixing block25, a stationary (non-rotatable) mixer element42, and an end plate43disposed on one end of the mixer element42for introducing the first and second liquids35,37into the mixing block25. The mixer element42is preferably a leftward or rightward twisted plate.

The first liquid35is forced from the first cylinder34through the end plate43into the mixing block25. Concurrently, the second liquid37is forced from the second cylinder36through the end plate43into the mixing block25.

The first and second liquids35,37are agitated and mixed together repeating a flow division, a rotational circulation and a flow reversal as the liquids35,37flow along the mixer element42. Since the static mixer41does not require the screw rotating mechanism27(FIG. 3), the mixing mechanism20is simple and cheap.

The injecting machine of the present invention is well suited for mixing and injecting first and second liquids of different properties.

Obviously, various minor changes and modifications of the present invention are possible in the light of the above teaching. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.