CA1110418A - Plastic injection molding machine including a defective molding detective device - Google Patents
Plastic injection molding machine including a defective molding detective deviceInfo
- Publication number
- CA1110418A CA1110418A CA296,055A CA296055A CA1110418A CA 1110418 A CA1110418 A CA 1110418A CA 296055 A CA296055 A CA 296055A CA 1110418 A CA1110418 A CA 1110418A
- Authority
- CA
- Canada
- Prior art keywords
- plunger
- limit value
- temperature
- presetting
- detecting device
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
- B29C45/17—Component parts, details or accessories; Auxiliary operations
- B29C45/76—Measuring, controlling or regulating
Landscapes
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Mechanical Engineering (AREA)
- Injection Moulding Of Plastics Or The Like (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A defective molding detecting device for a plastics injection molding machine, wherein at least two desirable points are present on the injection stroke of a plunger in the injection molding machine, the times during which the plunger passes through the respective points are measured, and a defective molding signal is sent out when the measured times deviate from the time allowances preset for the respective points. It is planned that said defective molding detecting device is used together with an off-temperature detecting device wherein the temperature at a desired preset point during molding cycle is measured and an off-temperature signal is sent out when said temperature measured deviates from the preset limit.
A defective molding detecting device for a plastics injection molding machine, wherein at least two desirable points are present on the injection stroke of a plunger in the injection molding machine, the times during which the plunger passes through the respective points are measured, and a defective molding signal is sent out when the measured times deviate from the time allowances preset for the respective points. It is planned that said defective molding detecting device is used together with an off-temperature detecting device wherein the temperature at a desired preset point during molding cycle is measured and an off-temperature signal is sent out when said temperature measured deviates from the preset limit.
Description
~10~'~8 B`ACKGROUND OF TEE~ INVENTION
-l. Field of the Invention . . .
This invention relates to a defective molding detecting device for a plastics injection molding machine, and in particular, to a defective molding detecting machine wherein defec-tive molding is determined by monitoring the length of time during which a plunger of the injection molding machine travels from one point to another within the injection stroke. '~
-l. Field of the Invention . . .
This invention relates to a defective molding detecting device for a plastics injection molding machine, and in particular, to a defective molding detecting machine wherein defec-tive molding is determined by monitoring the length of time during which a plunger of the injection molding machine travels from one point to another within the injection stroke. '~
2. Description of the-Prior Art In a plastics injection molding machine, a plunger travels from the injection starting position to the inject.ion ending position in the injection process. For example, if the injection start.inc~ position is PO and the .in~ect:ion ending position is PT .in Fi~. :1., then the plunger (not shown) trave:ls from PO to PT and return.s to PO upon the complet.ion o~ ~nolding.
Now, in the continuous operation under the same molding condition, as far as normal injection molding is effected, the relationship between the travelling distance and the time is substantiall~
constant in the injection stro]ce during which the plunger travels from the injection starting position to the injection endiny position. One example of said re.1.ationshlp is indicatect by a so:L:id line A in Fig. 2. For example, the time during which the plunger passes through a point Pl a distance Rl apart from the injection starting position PO is at a substantially constant value tl during continuous operation, the position of the plunger (the injection ending position PT) at the time of injection ending time to is substantially constant (the distance Ro)~ If defective molding is expected due to the mixiny of fo:reign matter 30 with resin, improper resin temperature or the :Li.ke, then the ''~
1 relationship between the travelling distance of the plunger and the time is not like the solid line A in Fig. 2, but like curved lines B and C, for example. The curved line B takes place when the plunger travels quick from some reason or other, and passes beyond the injection ending position PT depending upon the circumstances. The curved line C occurs when the plunger travels slow and does not reach the injection ending position PT at the time to. Consequently, defective molding can be determined by paying attention to the relationship between the travelling distance of the plunger and the time.
One of the conventional defective molding detecting devices comprises: a limit switch SO adapted -to be turned "ON"
when the plunger starts the injection; a switch Sl adapted to be tu~ned "ON" when the plunger passes through a des.ired point P1 located between PO and PT; and a switch SE adapted to be turned "ON" when the plunger passed beyond PT by a distance QE so as to detect the plunger having passed beyond PT; wherein said switches SO, Sl and SE have been arranged in the circuit arrange-ment shown in Fig. 3. Namely, designated at reference number 1 is a timer; and la a contact adapted to be turned "ON" when the timer is operated. Designated at 2, 3 and ~ are relays, res-pectively; 2a, 3a and ~a normally open contacts of the respective relays; and 3b a normally closed contact of the relay 3. L is a lamp for indicating the passage of the plunger through Pl.
In this conventional circuit, when the plunger starts travelling, firstly the switch SO is turned "ON" and the timer 1 is energized simultaneously with the start of travelling. Since the timer 1 set at a time tll a slightly lonaer than the timè tl durin~ which the plunger normally passes through the point Pl, the switch Sl is turned "ON" before the timer is operated to turn "ON" contact la, when molding is smoothly carried out. Then, the relay 3 1 is operated with its contact 3a being turned "ON" and self-holding, the contact 3b is turned "OFF", and thereafter the relay 2 is prevented from operating even if the con-tact la of the timer is turned "ON". `:
In the case the plunger travels slowly and the timer 1 is operated before the switch Sl is turned "ON", the relay 2 is energized via the contact la of the timer and the normally closed contact 3b of the relay 3 and operated. Then, the contact 2a thereof is turned "ON" to operate the relay 4, the contact 4a for self-holding is turned "ON", and the relay 4 sends out a defective molding signal, thereby operating an alarm, or :
operating a solenoid provided on a shooter for screening defective products. Additionally, in the c~s~ the plunger does not stop at the injection ending pos.it:ion PT and has reache~ PE, the switch SE is turned "ON" to operate the relay ~, whereby the same operations as above are performed. However, with this con-ventional defective molding detecting device, it has been judged ~- :
that, when the time during which the plunger passes through the point Pl is shorter than the preset time tll of the timer, it is normal one, and when the time is longer than the preset time, it is defective one. Namely, :referring to Fig. 2, if tll is regarded as tl, it has been judged that curves passing through a coordinate Yl or thereabove (for example, A and B) are normal ones and a curve passing under the coordinate Yl is de~ective one. However, although the curve A or a curve practically close to it are normal ones, the curve B is defective one. With the defective molding detecting device of the type described, it is 1 impossible to detect the defect caused by too ~uick movement of the plunger.
Additionally, such a defective molding detecting device has been known, wherein the measurement of time is started at the time when the liquid pressure of the piston for pressing the plunger has reached a predetermined level, the time is measured during which the plunger travels to the injection ending position, and, when thè measured time is off the preset time range, an alarm "excessively quick" or "excessively slow" is sent out.
Different from the aforementioned de~ective molding detectlng device, this defective molding detecting device can detect "excessively quick". However, said device is arranged such that the measurement of time is started at the time when the li~uid pressure ha~ reached the predetermined level. ~lence, there has been a dan~er o~ mal~unct:ion in case the viscosity oE mo:lcl;.ng material is changed d-lring the injection stroke, for example.
More detailed description will hereunder be given. As shown in Fig. 4, the relationship between the time and the pressure for injection during normal injection molding is indicated as ~, the ~ relationship between the time and the distance as K, and the t:ime during which the plunger reaches the injection ending position QO ater the injection pressure has reached the predetermined pressure hS as t21. In con-trast with the above, the re:Lation-ship between the time and the pressure is indicated as L in the case initially the viscosity o~ the molding material is low and the temperature of the metal mold is also low, or the vis-cosity o~ the molding material is low and the material fill opening of the metal mold is blocked with foreign matters, the relationship between the time and the distance in the above cases as M, and the measured time as t31. With the defective molding 4~L~
1 detecting devlce of -the type described, initially the viscosity of the material is low and the plunger travels quick. Accordingly, *he curve M is above the curve K. If the temperature of the metal mold is low, or the fill opening of t;he mold is blocked with foreign matters, where~y the plunger travels slow, and therefore, the curve M comes under the curve K, then the time during which the injection pressure reaches hS will lag by ~tl, and -the time during which the plunger reaches the injection ending position QO will lag by ~t2 also. If ~tl and at2 are substantially equal in value to each other, then t21 comes to be equal to t31, thereby unabling to detect defective molding.
SUMMAR~ OF THE INVENTION
-The object oE the present invention is to provicle a defec~ive molding detecting clevice capahle oE xol:iably cl~t~m:LnincJ
the defective molding ~y a plastics injection molding machine.
The defective molding detecting device according to the present invention comprises:
first measuring means for measuring the time during which the plunger passes through a first point preset on the injection stroke of the plunger;
means for presetting the upper limit value oE t:ime allowance corresponding to sai.d fi.rst point;
means for presetting the lower limit value of time allowance corresponding to said first point;
means for sending out a defective molding signal when the time measured by said first measuring means deviates from the range between said upper and lower limit values corresponding thereto;
second measuring means for measuring the time during which the plunger passed through a second point preset on the injection 41~
1 stroke of the plunger which is other than said first point;
means for presetting the upper limit value of time allowance corresponding to said second point;
means for presetting the lower limit ~alue of time allowance corresponding to said second point; and means for sending out a defective molding signal when the time measured by said second measuring means deviates from the range between said upper and lower limit values corresponding thereto.
The measurements of times by said first and second measurlng means are started when the plunger starts from the injection starting position or when the plunger passes through a point, respectively. It is preferable that said first and second measuring means are consist oE counters Eor count.ing clock pulses fed simultaneously with the startincl of the measurement of time, reE;pect:ive:Ly, while means for presetting the uppermost values and lowermost ~alues corresponding to said first and second points consist of digital switches, respectively.
It is desirable that means be provided for indicating the times measured by said first and second measuring means.
The temperature of the metal mold into which p:Lastics material is filled is one of the important factors in molding.
The temperature oE the metal mold changes a:Long with filing the resin thereinto. In the case of repeated production of the same sort of molding products, the temperature of a definite point of the metal mold during the molding cycle is constant. For example, the time between the first starting of injection and next starting of injection hy the plunger (screw) is regarded as one cycle of molding, the temperature at a definite point during each cycle is substantially constant.
1 Therefore, it is preferable to monitor the temperature at a definite point within the molding cycle in addition to monitoring by the measurements of time. For this reason, it is desirable to provide: means for detecting the temperature at a desired point of the mold during the molding cycle; means ~or presetting the upper limit value of the temperature of the mold; means for presetting the lower limit value of the temperature of the mold;
and means for sending out a mold off-temperature signal when the measured mold temperature deviates from the range between said upper and lower limit values of the preset temperature. It is desirable that said mold temperature detecting means is adapted to send out a signal of the temperature detected as a digital value, while the means for presetting the upper and lower limit values of the mold temperature consist oE digital presetting means, respectivel~. ~t is a:lso clesirablc to prov:ide me~ns eOx indicating the temperature detected ~ the molcl temperature detecting means as a digital value.
BRIEF DESCRI~?TION OF THE DRAWINGS
The above mentioned and other features and objects of the present invention will becomq more apparent by re~erence to the following description taken in conjunction with the accompany-ing drawings, wherein like reEerence numerals denote like elements, and in which:
Fig. 1 is a chart showing the positional relationship of the switches provided for detecting the position of the plunger in the conventional defective molding detecting device;
Fig. 2 is a chart showin~ the relationship between the travelling distance and the time of the plunger in the con ventional example;
1 Fig. 3 is a circuit diagram of the conventional defective molding detecting device;
Fig. 4 is a chart showing the relationships between the injection pressure and the time and between the travelling ;
distance and the time in the conventional example;
Fig. 5 and Fig. 6 are views showing the positional relationships of the switches in one embodiment of the present invention;
Fig. 7 is a chart showing the relationskip between the travelling distance and the time of the plunger in explanation of the operation of the embodiment, Fig. 8 is an electrical circuit diagram of the defective molding detecting device embodying the present invention;and Fig. 9 is an electrical c:ircuit diagram the means oE
detecting an off-temperature O:e the mold at a deE:inite po:int during the molding cycle.
DESCRIPTION OF THE Il`lVENTION
. ~
In Fig. 5, designated at reference numeral 34 is a front mold mounted on a fixed plate 35. 36 is a movable mold mounted on a movable plate 37. The front mold 34 is provided therein with a communicating port 40 communicated with a nozzle portion 39 oE an injection cylinder 38, 41 is a hopper for ' a plastics material which is provided at the intermediate portion of the injection cylinder. One end of the plunger 42 is formed into a piston 43. Said piston 43 is inserted into a hydraulic cylinder 44, whereby the plunger 42 is adapted to move backward and forward in the injection cylinder 38. The plunger 42 is adapted to be rotated by a driving mechanism such as an el~ctric motor (not shown~. 45 is a ring fixed on the intermediate portion of the plunger 42. Limit switches SO, 4~18 1 S1, S2 operated by said ring 45 are disposed along the stroke o the plunger 42. The positional relationship of said limit switches SO, Sl, S2 is detailedly shown in Fig. 6. A point Pl a distance 11 apart from PO and another point P2 a distance 12 apart from PO are preset between the injection starting point PO and.the injection ending position PT of the plunger, and the switches S1 and S2 are provided which are adapted to be switched from "OFF" to "ON" when the plunger passed through the respective points in the arrow-marked direction. As described above, said switch SO is also adapted to be switched from "OFF" to "ON" at the same time as the plunger starts the injection. Said switch SO may be disposed at a position a predetermined distance advanced toward Pl from the injection starting position of the p:lunger 80 aæ to ~tart the time measurement after the injection starting. Further, the posit:ions and number o~ th~ preset points for the time measuremen-t may be desirably selected depending upon the molding condition. 5 is a pulse oscillator oscillating at a definite period. A pulse sent out ~y said pulse oscillator is fed to a counter 7 through an .inhibit gate 6 adapted to close the gate by "ON" signals from the switches SO, Sl. 8 is an indicator for digitally indicating a count number Xl o~ the counter 7. Likewise, 9 :is an inhibit yate adapted to close the gate ~y an "ON" signal o the switch S2, 10 a counter, 11 an indicator or indicating a count number X2 of the counter 1~. An output pulse from the pulse oscillator 5 is adapted to be ed to the counter 10 through the inhibit gate 9. 12, 13, 14, 15 are digital presetters. 12 presets the lower limit value D, the time at which the plunger passes through the preset point Pl, 13 the upper limit value thereo, 14 the lower limit
Now, in the continuous operation under the same molding condition, as far as normal injection molding is effected, the relationship between the travelling distance and the time is substantiall~
constant in the injection stro]ce during which the plunger travels from the injection starting position to the injection endiny position. One example of said re.1.ationshlp is indicatect by a so:L:id line A in Fig. 2. For example, the time during which the plunger passes through a point Pl a distance Rl apart from the injection starting position PO is at a substantially constant value tl during continuous operation, the position of the plunger (the injection ending position PT) at the time of injection ending time to is substantially constant (the distance Ro)~ If defective molding is expected due to the mixiny of fo:reign matter 30 with resin, improper resin temperature or the :Li.ke, then the ''~
1 relationship between the travelling distance of the plunger and the time is not like the solid line A in Fig. 2, but like curved lines B and C, for example. The curved line B takes place when the plunger travels quick from some reason or other, and passes beyond the injection ending position PT depending upon the circumstances. The curved line C occurs when the plunger travels slow and does not reach the injection ending position PT at the time to. Consequently, defective molding can be determined by paying attention to the relationship between the travelling distance of the plunger and the time.
One of the conventional defective molding detecting devices comprises: a limit switch SO adapted -to be turned "ON"
when the plunger starts the injection; a switch Sl adapted to be tu~ned "ON" when the plunger passes through a des.ired point P1 located between PO and PT; and a switch SE adapted to be turned "ON" when the plunger passed beyond PT by a distance QE so as to detect the plunger having passed beyond PT; wherein said switches SO, Sl and SE have been arranged in the circuit arrange-ment shown in Fig. 3. Namely, designated at reference number 1 is a timer; and la a contact adapted to be turned "ON" when the timer is operated. Designated at 2, 3 and ~ are relays, res-pectively; 2a, 3a and ~a normally open contacts of the respective relays; and 3b a normally closed contact of the relay 3. L is a lamp for indicating the passage of the plunger through Pl.
In this conventional circuit, when the plunger starts travelling, firstly the switch SO is turned "ON" and the timer 1 is energized simultaneously with the start of travelling. Since the timer 1 set at a time tll a slightly lonaer than the timè tl durin~ which the plunger normally passes through the point Pl, the switch Sl is turned "ON" before the timer is operated to turn "ON" contact la, when molding is smoothly carried out. Then, the relay 3 1 is operated with its contact 3a being turned "ON" and self-holding, the contact 3b is turned "OFF", and thereafter the relay 2 is prevented from operating even if the con-tact la of the timer is turned "ON". `:
In the case the plunger travels slowly and the timer 1 is operated before the switch Sl is turned "ON", the relay 2 is energized via the contact la of the timer and the normally closed contact 3b of the relay 3 and operated. Then, the contact 2a thereof is turned "ON" to operate the relay 4, the contact 4a for self-holding is turned "ON", and the relay 4 sends out a defective molding signal, thereby operating an alarm, or :
operating a solenoid provided on a shooter for screening defective products. Additionally, in the c~s~ the plunger does not stop at the injection ending pos.it:ion PT and has reache~ PE, the switch SE is turned "ON" to operate the relay ~, whereby the same operations as above are performed. However, with this con-ventional defective molding detecting device, it has been judged ~- :
that, when the time during which the plunger passes through the point Pl is shorter than the preset time tll of the timer, it is normal one, and when the time is longer than the preset time, it is defective one. Namely, :referring to Fig. 2, if tll is regarded as tl, it has been judged that curves passing through a coordinate Yl or thereabove (for example, A and B) are normal ones and a curve passing under the coordinate Yl is de~ective one. However, although the curve A or a curve practically close to it are normal ones, the curve B is defective one. With the defective molding detecting device of the type described, it is 1 impossible to detect the defect caused by too ~uick movement of the plunger.
Additionally, such a defective molding detecting device has been known, wherein the measurement of time is started at the time when the liquid pressure of the piston for pressing the plunger has reached a predetermined level, the time is measured during which the plunger travels to the injection ending position, and, when thè measured time is off the preset time range, an alarm "excessively quick" or "excessively slow" is sent out.
Different from the aforementioned de~ective molding detectlng device, this defective molding detecting device can detect "excessively quick". However, said device is arranged such that the measurement of time is started at the time when the li~uid pressure ha~ reached the predetermined level. ~lence, there has been a dan~er o~ mal~unct:ion in case the viscosity oE mo:lcl;.ng material is changed d-lring the injection stroke, for example.
More detailed description will hereunder be given. As shown in Fig. 4, the relationship between the time and the pressure for injection during normal injection molding is indicated as ~, the ~ relationship between the time and the distance as K, and the t:ime during which the plunger reaches the injection ending position QO ater the injection pressure has reached the predetermined pressure hS as t21. In con-trast with the above, the re:Lation-ship between the time and the pressure is indicated as L in the case initially the viscosity o~ the molding material is low and the temperature of the metal mold is also low, or the vis-cosity o~ the molding material is low and the material fill opening of the metal mold is blocked with foreign matters, the relationship between the time and the distance in the above cases as M, and the measured time as t31. With the defective molding 4~L~
1 detecting devlce of -the type described, initially the viscosity of the material is low and the plunger travels quick. Accordingly, *he curve M is above the curve K. If the temperature of the metal mold is low, or the fill opening of t;he mold is blocked with foreign matters, where~y the plunger travels slow, and therefore, the curve M comes under the curve K, then the time during which the injection pressure reaches hS will lag by ~tl, and -the time during which the plunger reaches the injection ending position QO will lag by ~t2 also. If ~tl and at2 are substantially equal in value to each other, then t21 comes to be equal to t31, thereby unabling to detect defective molding.
SUMMAR~ OF THE INVENTION
-The object oE the present invention is to provicle a defec~ive molding detecting clevice capahle oE xol:iably cl~t~m:LnincJ
the defective molding ~y a plastics injection molding machine.
The defective molding detecting device according to the present invention comprises:
first measuring means for measuring the time during which the plunger passes through a first point preset on the injection stroke of the plunger;
means for presetting the upper limit value oE t:ime allowance corresponding to sai.d fi.rst point;
means for presetting the lower limit value of time allowance corresponding to said first point;
means for sending out a defective molding signal when the time measured by said first measuring means deviates from the range between said upper and lower limit values corresponding thereto;
second measuring means for measuring the time during which the plunger passed through a second point preset on the injection 41~
1 stroke of the plunger which is other than said first point;
means for presetting the upper limit value of time allowance corresponding to said second point;
means for presetting the lower limit ~alue of time allowance corresponding to said second point; and means for sending out a defective molding signal when the time measured by said second measuring means deviates from the range between said upper and lower limit values corresponding thereto.
The measurements of times by said first and second measurlng means are started when the plunger starts from the injection starting position or when the plunger passes through a point, respectively. It is preferable that said first and second measuring means are consist oE counters Eor count.ing clock pulses fed simultaneously with the startincl of the measurement of time, reE;pect:ive:Ly, while means for presetting the uppermost values and lowermost ~alues corresponding to said first and second points consist of digital switches, respectively.
It is desirable that means be provided for indicating the times measured by said first and second measuring means.
The temperature of the metal mold into which p:Lastics material is filled is one of the important factors in molding.
The temperature oE the metal mold changes a:Long with filing the resin thereinto. In the case of repeated production of the same sort of molding products, the temperature of a definite point of the metal mold during the molding cycle is constant. For example, the time between the first starting of injection and next starting of injection hy the plunger (screw) is regarded as one cycle of molding, the temperature at a definite point during each cycle is substantially constant.
1 Therefore, it is preferable to monitor the temperature at a definite point within the molding cycle in addition to monitoring by the measurements of time. For this reason, it is desirable to provide: means for detecting the temperature at a desired point of the mold during the molding cycle; means ~or presetting the upper limit value of the temperature of the mold; means for presetting the lower limit value of the temperature of the mold;
and means for sending out a mold off-temperature signal when the measured mold temperature deviates from the range between said upper and lower limit values of the preset temperature. It is desirable that said mold temperature detecting means is adapted to send out a signal of the temperature detected as a digital value, while the means for presetting the upper and lower limit values of the mold temperature consist oE digital presetting means, respectivel~. ~t is a:lso clesirablc to prov:ide me~ns eOx indicating the temperature detected ~ the molcl temperature detecting means as a digital value.
BRIEF DESCRI~?TION OF THE DRAWINGS
The above mentioned and other features and objects of the present invention will becomq more apparent by re~erence to the following description taken in conjunction with the accompany-ing drawings, wherein like reEerence numerals denote like elements, and in which:
Fig. 1 is a chart showing the positional relationship of the switches provided for detecting the position of the plunger in the conventional defective molding detecting device;
Fig. 2 is a chart showin~ the relationship between the travelling distance and the time of the plunger in the con ventional example;
1 Fig. 3 is a circuit diagram of the conventional defective molding detecting device;
Fig. 4 is a chart showing the relationships between the injection pressure and the time and between the travelling ;
distance and the time in the conventional example;
Fig. 5 and Fig. 6 are views showing the positional relationships of the switches in one embodiment of the present invention;
Fig. 7 is a chart showing the relationskip between the travelling distance and the time of the plunger in explanation of the operation of the embodiment, Fig. 8 is an electrical circuit diagram of the defective molding detecting device embodying the present invention;and Fig. 9 is an electrical c:ircuit diagram the means oE
detecting an off-temperature O:e the mold at a deE:inite po:int during the molding cycle.
DESCRIPTION OF THE Il`lVENTION
. ~
In Fig. 5, designated at reference numeral 34 is a front mold mounted on a fixed plate 35. 36 is a movable mold mounted on a movable plate 37. The front mold 34 is provided therein with a communicating port 40 communicated with a nozzle portion 39 oE an injection cylinder 38, 41 is a hopper for ' a plastics material which is provided at the intermediate portion of the injection cylinder. One end of the plunger 42 is formed into a piston 43. Said piston 43 is inserted into a hydraulic cylinder 44, whereby the plunger 42 is adapted to move backward and forward in the injection cylinder 38. The plunger 42 is adapted to be rotated by a driving mechanism such as an el~ctric motor (not shown~. 45 is a ring fixed on the intermediate portion of the plunger 42. Limit switches SO, 4~18 1 S1, S2 operated by said ring 45 are disposed along the stroke o the plunger 42. The positional relationship of said limit switches SO, Sl, S2 is detailedly shown in Fig. 6. A point Pl a distance 11 apart from PO and another point P2 a distance 12 apart from PO are preset between the injection starting point PO and.the injection ending position PT of the plunger, and the switches S1 and S2 are provided which are adapted to be switched from "OFF" to "ON" when the plunger passed through the respective points in the arrow-marked direction. As described above, said switch SO is also adapted to be switched from "OFF" to "ON" at the same time as the plunger starts the injection. Said switch SO may be disposed at a position a predetermined distance advanced toward Pl from the injection starting position of the p:lunger 80 aæ to ~tart the time measurement after the injection starting. Further, the posit:ions and number o~ th~ preset points for the time measuremen-t may be desirably selected depending upon the molding condition. 5 is a pulse oscillator oscillating at a definite period. A pulse sent out ~y said pulse oscillator is fed to a counter 7 through an .inhibit gate 6 adapted to close the gate by "ON" signals from the switches SO, Sl. 8 is an indicator for digitally indicating a count number Xl o~ the counter 7. Likewise, 9 :is an inhibit yate adapted to close the gate ~y an "ON" signal o the switch S2, 10 a counter, 11 an indicator or indicating a count number X2 of the counter 1~. An output pulse from the pulse oscillator 5 is adapted to be ed to the counter 10 through the inhibit gate 9. 12, 13, 14, 15 are digital presetters. 12 presets the lower limit value D, the time at which the plunger passes through the preset point Pl, 13 the upper limit value thereo, 14 the lower limit
3~ value, the time at which the plun~er passes through the preset 1 point P2, and 15 the upper limit value thereo~ 16~ 17 are multiplexers, and 18 a subtracter. Upon receiving a t;Lming signal TM, the multiplexer 17 selectively switches in sequential order the values D - G preset by the digital presetters 12 - 15 to feed to the subtracter 18 for example and repeats the action described above. Likewise, the multiplexer 16, when the preset value (D or E) of the digital presetter 12 or 13 is selected~
selects the count number Xl and sends the same to subtracter 18, whereas, when the preset value (F or G) of the digital presetter 14 or 15 is selected, selects the count number X2 of the counter 10 and sends the same to the subtracter 18, and repeats the action described above. The subtracter 18 subtracts the preset value of the digital presetters 12 - 15 from the count number of the counter 7 or :L0, bein~ synchronLzed with the timing si~nal.
Namely, the subtracter 1~ repeateclly perEorms the subtrclctions - of four types including Xl - D, Xl - E, X2 - F and X2 - G in sequential order, being synchronized with the timing signal.
The order of the subtractions of said four types is not necessarily limited to the above only. 19 a circuit for judging the result of subtraction, whether it is plus or minus, and, :likewise, is synchronized with the timing signal TM. 20 is a de-multiplexer, And 21 - 2~ are latch circuits. The de-multiplexer 20 is adapted to switch the respective judged results on the sub~
tractions of four types judged by the judging circuit 19 to the respective latch circuits corresponding thereto. Accordingly, when the subtracter 18 performed the calculation of Xl ~ D and the result is judged to be plus or minus for example, the result judged is held by the latch circuit 21, next, the subtracter 18 performs the calculation of Xl - E and the result is judged to be plus or minus and the result is held by the latch circuit 22, likewise, the result of calculation o X2 - F, plus or minus is held by the latch circuit 23, and the judged result of the calculation of X2 - G, plus or minus, is held by the latch circuit 24, respectively. Said latch circuits 21 - 24, when the judged result is plus, are adapted to send out "1", and when the judged result is minus, send out "O", for example, when the judged result changes, the outputs are adapted to change also.
25 is a NOT gate ~or reversing an output of the latch circuit 21, and 26 an AND gate for receiving an output from the NOT gate 25 r 10 and an output from the switch Sl, and is adapted to send out an output, when the time during which the plunger passed through the preset point Pl is shorter than the lower limit value D.
27 is an inhibik gate, when the switch Sl sends out no output, and the latch circuit 22 sends out "1", sends out an output, and, when khe time during which the plunger passes through the preset point Pl is longer than the upper limit value E, is adapted to send out an output. Likewise, 28 is a NOT gate for reversing an output from the latch circuit 23, and 29 an AND gate for receiving an output from the NOT gate 28 and an output from the switch S2 and is adapted to send out an output when the time during which the plunger passes through the preset point P2 is shorter than the lower limit value F. 30 is an inhibit gate, when the switch S2 sends out no output, and the latch circuit 2 sends out "1", sends out an output, and when the time at which the plunger passes through the preset point P2 is longer than the upper limit value G, is adapted to send out an output. 31 is an OR gate, and 32 a latch circuit for holding an output from the OR gate 31 and sending out a defective molding signal W.
33 is a switch for resetting the latch circuit 32. Said ~C switch 33 may be a manual switch or a switch 41~
1 associated with a timer for controlling the molding machine in such a manner that, a defective molding signal is sent out from the latch circuit 32 only in the molding cycle during which an unusual condition occurs. Description will be given of the operation of said circuit. Firstly, the - lla -<
1 upper limit values and the lower limit values D, E, F, G for the preset points Pl, P2 are preset, respectively, by the digital presetters 12 - 15, and then, the injection molding machine is started to operate. Upon the injection starting of th~ plunger, the switch ~0 is turned "ON", and pulses are fed to the counters 7 and 10 via the inhibit gates 6, 9. Upon receiving timing signals, the multiplexers 16, 17, de-multiplexer 20, subtracter 18 and plus-minus judging circuit 19 the following performances are effected which include the reading of the counter numbers Xl, or X2 of the counters 7 or 10, reading of the preset values of the digital presetters 12 - 15, subtraction, plus-minus judging, and allocation of the judged results to the corresponding latch circu.its 21 - 2~. The above operation ~rom the readincJ to allocation is repe~ted~:Ln pursuit of the increases oE
the count numbers Xl and X2 with the lapse of time.
Since the switch Sl is "OFF" (S2 naturally is "OFF" also) until the plunger passes through the preset point Pl, the AND gates 26, 29 send out no outputs. Additionally, when the molding is normally carried out, -the count num~er Xl does not exceed the upper limit value F which is preset for Pl beEore the plunger passes through the preset point Pl. ~lence, the latch circuit 22 sends out an output "O" (The latch circuit 2~ naturally sends out an output "O" also). Consequently, the inhibit gates 27, 30 send out no output. When the plunger passes through the point Pl, the switch Sl is turned "ON". By this, the inhibit gate 6 is closed, the counting action by the counter 7 is interrupted, and the count number is indicated by the indicator 8. At this -time, if Xl is larger than the lower limit value D, then an output "1" of the latch circuit 21 is reversed by the NOT gate 25. Hence, even if the switch Sl is turned on, the AND ga-te 26 se~ds out no output. In this case, if Xl is less than the upper 1 limit value El -then the latch circuit 22 sends out an output "O", and the inhibit gate 27 sends out no output. Therefore, suppose the time during which the plunger passes through the point Pl is Xll, if Xll remains within the range of D <Xll<E, the AND gate 26 and inhibit gate 27 send out no output. In contrast with this, if D>Xll, the latch circuit 21 sends out an output "O" which is reversed by the NOT gate. Hence, the AND
gate 26 sends out an output which operates the latch circuit 32 to send out a defective molding signal W. Further if Xll>E, 0 the latch circuit 22 sends out an output "1" to the OR gate 31 before the switch Sl is turned "ON". Hence, said output "1" operates the latch circuit 32 to send ou-t a defecti.ve molding signal W. Even i:E the plunger does not reach the point Pl and stops shor~ of the point Pl, the latch circuit 22 sends out an output "1", and l.ikewise, a de~ective molding s:ignal W
is sent out. In the case the plunger passed through -the point Pl and thereafter passes through the point P2, if the time during which the plunger passes through the point P2 is X22, a de-fectlve :~
molding signal W is not sent out as long as F<X22_G. When F>X22 or X22>G, the AND gate 29 or inhibit gate 30 sends out an output to operate the latch circuit 32 to send out a defective molding signal W. As described above, according to the present embodiment, when the respective times during which the plunger passes through the preset points Pl, P2, respectively, are not within the ranges between the upper and lower limit values pre-determined for the preset values Pl, P2, respectively, then a defective molding signal W is sent out. Hence, said signal can operate an alarm, or operate a solenoid of the shooter to screen defective products. Namely, in the case the relationship between the travelling distance of the plunger and the time is same as ,~.
. .
1 the curve shown in Fig. 7A, a defective molding signal W is not sent out. In the case of Fig. 7B, 7C or 7H, a defective molding signal W is sent out. According to the present embodiment, the times during which the plunger passes the points Pl, P2, respectively, are indicated by the indicators 8, 11. Hence, the .
indication can be utilized for judging the quality of defect;ve products or the quality of goods products. Further, the upper and lower limit values can be desirably selected ~y.the digi.tal presetters 12 - 15.
Fig. 9 sho~sa circuit for measuring the temperature at a definite point of the mold wi-thin the molding cycle. Said circuit is used together with the circuit s~lown in Fig, 8 for example, so that the judgement of deEect:ive mold:;n~ can ~e per-formed more reliabl~. ~n FicJ. 9, the Eront mold 3~ .is penetra-tingl~ prov:icled w:ith a hole 47 ad.jclcent to a space ~6.
thermoresistance 48 such as a thermister is installed on the bottom of said hole\ 47. 49 is a resistance-voltage converter for converting the resistance value of a temperature measuring resistor 48 into voltage of the resistance-voltage converter 4~
is fed to and held by a sample holding circuit 50. Said sample holding circuit 5~ is adapted to hold a voltage fed from the resistance-voltagè conv~rter 4J, receiving a timi.ng pulse T
from a timing generator 51. The voltage value.held ~y the sample holding circuit 50 ~y the timing pulse Tl from the timing generator 51 is converted to a pulse corresponding in number to the voltage value by a voltage-frequency converter 52. The pulse from the voltage-frequency converter 52 is adapted to ~e fed to a counter 54 through a gate 53 which is opened commensurate to the pulse width of a timing pulse T2 sent out from the timing generator 51. The counter 54 is adapted to be reset hy a timing pulse T3 from the timing generator 51 immediately before the gate g 53 is opened by the timing pulse T2. A pulse fed to the counter 54 through the gate 53 after the counter 54 is reset by the timing pulse T3 is counted ~y the counter 54, and the count number is digitally indicated ~y an indicator 55 The timing generator 51 adapted to repeatedly send out the timing pulses Tl, T2, T3. Only when receiving a pulse signal TS from a pulse generator 56 which will be descrihed hereinafter, the timing generator 51 sends out Tl, T2, T3 each once~ and then f sends out a starting pulse T4 once for a comparator which will ~e described hereinafter. SO is the aforesaid limit switch disposed at a position PO suitable for sending out a signal when the plunger starts from the injection starting position. Said limit switch SO may ~e disposed at a position, for example, shown ~y dot~ed lines in the draw.ing, so that ~he sw:itch can send out a signal when the plunger passes through a po;int a predetcrmine(l distance advanced from the injection starting position. Namely, it can be desirably selected that at what posi-tion in the molding cycl~ the limit switch SO sends out a signal. A si.gnal rom the switch SO is fed to a pulse generating circuit 56 comprising a differentiation circuit and a monostable multivibrator, converted into a pulse signal Ts, and sent to the timing generator 51 through a manual switch 57. 58 and 59 are digita:l. presetters for presetting the upper and :Lower limi.t values o:E the mold tem~
perature, and each comprises a dial type digital switch, for example. 60 and 61 are comparators for comparing the digital values in magnitude. The comparator 60 is adapted to compare the upper limit value of the mold temperature preset hy the digital presetter 58 with the count number of the counter 54 upon receiving a timing pulse T~ from the timing generator 51, and send out a mold off-temperature signal when the count number 34~8 1 of the counter 54 is larger than the upper limit value preset by the digital presetter 58. Additionally, the comparator 61 is adap-ted to compare the count number of the counter 54 with the lower limit value prese-t by the digital presetter 59 upon receiving a timing pulse T4, and send out a mold off-temperature signal when the count number of the counter 54 is less than the lower limit value preset by the digital presetter 59. A mold off-temperature signal sent out from the comparator 60 or 61 is fed to the latch circuit 63 through an OR gate 62 and held 1~ thereby. 64 is a switch similar to said sw:itch 33 for resetting the latch circuit 63.
Description will hereunder be given of the operation of the present embodiment. The temperature of the mold 34 variable during molding cycle is continuously detectecl b~ the temperature measuriny re~,istor ~. The va:Lue~ thus detected :is conv~rted into voltage by the resistance-voltage converter 49, and ~urther, is held by the sample holding circuit 50. The voltage held by the sample holding circuit 50 and commensurate to the mold ` temperature is converted into a pulse by the voltage-frequency converter 52, and fed to the counter 54 through the gate 53 and counted. The count number of the counter 54 is indicated by the indicator 55. Accordingly, if the sw:itch 57 is "OFF", then the mold temperature variable with:in rnolding cycle can be detectecl and digitally indicated by the temperature measuring resi.stor 48 and the indicator 55, respectively. In order to detect -the mold of~-temperature, it lS necessary to preset values in the digital presetters 58, 59 and turn the switch "ON". When the plastici-zation of a resin material is completed, the plunger 42 is advanced to the injection starting position by the hydraulic pressure in a cylinder 44 as indicated by an arrow mark .in the 9LiL~
1 drawing and the ring 45 mounted on a plunger 42 leaves the limit switch SO, whereby said limit switch sends out a signal. This signal causes the pulse generator 56 to generate a pulse Ts.
When said pulse signal TS is fed to the timing circuit 51, said timing circuit 51 sends out timing pulses Tl, T~, T3, T4 each once. Accordingly, the sample holding circuit 50 holds a tem-perature signal at the injection starting time until the succeeding injection starting time, and in corresponding thereto, the counter 54 and the indicator 55 hold and indicate the tem-tO perature until the succeeding injection starting time, respectively.Further, the comparator 60 compares the count number of the counter 54 with the value preset by the digital presetter 58 by use of the timing pulse T~, when the count number of the counter 5~ is less, sends out no output, and, when the count number o~ the counter 5~ is larger than the upper lim:it ~alue preset, sends out an off-temperature signal. Additionally,the comparator 61 compares the count number of the counter 5~ with the lower limit value of the mold temperature preset by the digital presetter 59 by use of the timing signal T~, when the count number of the counter 5~ is larger, sends out no output, and when the count number of the counter 5~ is :Less than the lower limit value, sends out an oEE-temperature si~nal. When either the comparatox 60 or 61 sends out an off-temperature, said signal is fed to a latch circuit 63 through an OR gate 62 and held thereby. The off-temperature signal held by the latch circuit 63 is further sent out to outside, and used as a signal for operating an alarm or the like, for example. According to the present embodiment, if the switch 57 is kept "OFE", then~the mold temperature varying from time to time during molding cycle is digitally indicated by the indicator 55. Additionally, if 1 the switch 57 is kept "ON" and the upper and lower limit values of the mold temperature at the injection starting time are preset by the digital presetters 58 and 59, then the mold temperatures at the injection starting times during the respective molding cycles are indicated~ And at the same time, comparison is made between the mold temperature at the injection starting time in every molding cycle and the upper and lower limit values preset by the digital presetters 58 and 59, an off-temperature signal is sent out when the mold temperature measured at the injection 1~ starting time is not in the range between the upper and lower limit values. In addition, if the limit switch SO is disposed at a new point a predetermined dis-tance advanced from the position PO and the upper and lower limi.t values are preset accordin~ then the mo:ld temperature at the new po.int can be ind.icated, and the detection is made as to whether the mold temperature at the new point is off or not. As described above, the point at which off-temperature is detected in molding cycle may be desirably selected, and may be selected at two or more points. For a signal fed to pulse generator 56, the signal at the time of opening the mold 36 may be used. Further, it is possible to use a thermocouple for measuring the mold temperature.
selects the count number Xl and sends the same to subtracter 18, whereas, when the preset value (F or G) of the digital presetter 14 or 15 is selected, selects the count number X2 of the counter 10 and sends the same to the subtracter 18, and repeats the action described above. The subtracter 18 subtracts the preset value of the digital presetters 12 - 15 from the count number of the counter 7 or :L0, bein~ synchronLzed with the timing si~nal.
Namely, the subtracter 1~ repeateclly perEorms the subtrclctions - of four types including Xl - D, Xl - E, X2 - F and X2 - G in sequential order, being synchronized with the timing signal.
The order of the subtractions of said four types is not necessarily limited to the above only. 19 a circuit for judging the result of subtraction, whether it is plus or minus, and, :likewise, is synchronized with the timing signal TM. 20 is a de-multiplexer, And 21 - 2~ are latch circuits. The de-multiplexer 20 is adapted to switch the respective judged results on the sub~
tractions of four types judged by the judging circuit 19 to the respective latch circuits corresponding thereto. Accordingly, when the subtracter 18 performed the calculation of Xl ~ D and the result is judged to be plus or minus for example, the result judged is held by the latch circuit 21, next, the subtracter 18 performs the calculation of Xl - E and the result is judged to be plus or minus and the result is held by the latch circuit 22, likewise, the result of calculation o X2 - F, plus or minus is held by the latch circuit 23, and the judged result of the calculation of X2 - G, plus or minus, is held by the latch circuit 24, respectively. Said latch circuits 21 - 24, when the judged result is plus, are adapted to send out "1", and when the judged result is minus, send out "O", for example, when the judged result changes, the outputs are adapted to change also.
25 is a NOT gate ~or reversing an output of the latch circuit 21, and 26 an AND gate for receiving an output from the NOT gate 25 r 10 and an output from the switch Sl, and is adapted to send out an output, when the time during which the plunger passed through the preset point Pl is shorter than the lower limit value D.
27 is an inhibik gate, when the switch Sl sends out no output, and the latch circuit 22 sends out "1", sends out an output, and, when khe time during which the plunger passes through the preset point Pl is longer than the upper limit value E, is adapted to send out an output. Likewise, 28 is a NOT gate for reversing an output from the latch circuit 23, and 29 an AND gate for receiving an output from the NOT gate 28 and an output from the switch S2 and is adapted to send out an output when the time during which the plunger passes through the preset point P2 is shorter than the lower limit value F. 30 is an inhibit gate, when the switch S2 sends out no output, and the latch circuit 2 sends out "1", sends out an output, and when the time at which the plunger passes through the preset point P2 is longer than the upper limit value G, is adapted to send out an output. 31 is an OR gate, and 32 a latch circuit for holding an output from the OR gate 31 and sending out a defective molding signal W.
33 is a switch for resetting the latch circuit 32. Said ~C switch 33 may be a manual switch or a switch 41~
1 associated with a timer for controlling the molding machine in such a manner that, a defective molding signal is sent out from the latch circuit 32 only in the molding cycle during which an unusual condition occurs. Description will be given of the operation of said circuit. Firstly, the - lla -<
1 upper limit values and the lower limit values D, E, F, G for the preset points Pl, P2 are preset, respectively, by the digital presetters 12 - 15, and then, the injection molding machine is started to operate. Upon the injection starting of th~ plunger, the switch ~0 is turned "ON", and pulses are fed to the counters 7 and 10 via the inhibit gates 6, 9. Upon receiving timing signals, the multiplexers 16, 17, de-multiplexer 20, subtracter 18 and plus-minus judging circuit 19 the following performances are effected which include the reading of the counter numbers Xl, or X2 of the counters 7 or 10, reading of the preset values of the digital presetters 12 - 15, subtraction, plus-minus judging, and allocation of the judged results to the corresponding latch circu.its 21 - 2~. The above operation ~rom the readincJ to allocation is repe~ted~:Ln pursuit of the increases oE
the count numbers Xl and X2 with the lapse of time.
Since the switch Sl is "OFF" (S2 naturally is "OFF" also) until the plunger passes through the preset point Pl, the AND gates 26, 29 send out no outputs. Additionally, when the molding is normally carried out, -the count num~er Xl does not exceed the upper limit value F which is preset for Pl beEore the plunger passes through the preset point Pl. ~lence, the latch circuit 22 sends out an output "O" (The latch circuit 2~ naturally sends out an output "O" also). Consequently, the inhibit gates 27, 30 send out no output. When the plunger passes through the point Pl, the switch Sl is turned "ON". By this, the inhibit gate 6 is closed, the counting action by the counter 7 is interrupted, and the count number is indicated by the indicator 8. At this -time, if Xl is larger than the lower limit value D, then an output "1" of the latch circuit 21 is reversed by the NOT gate 25. Hence, even if the switch Sl is turned on, the AND ga-te 26 se~ds out no output. In this case, if Xl is less than the upper 1 limit value El -then the latch circuit 22 sends out an output "O", and the inhibit gate 27 sends out no output. Therefore, suppose the time during which the plunger passes through the point Pl is Xll, if Xll remains within the range of D <Xll<E, the AND gate 26 and inhibit gate 27 send out no output. In contrast with this, if D>Xll, the latch circuit 21 sends out an output "O" which is reversed by the NOT gate. Hence, the AND
gate 26 sends out an output which operates the latch circuit 32 to send out a defective molding signal W. Further if Xll>E, 0 the latch circuit 22 sends out an output "1" to the OR gate 31 before the switch Sl is turned "ON". Hence, said output "1" operates the latch circuit 32 to send ou-t a defecti.ve molding signal W. Even i:E the plunger does not reach the point Pl and stops shor~ of the point Pl, the latch circuit 22 sends out an output "1", and l.ikewise, a de~ective molding s:ignal W
is sent out. In the case the plunger passed through -the point Pl and thereafter passes through the point P2, if the time during which the plunger passes through the point P2 is X22, a de-fectlve :~
molding signal W is not sent out as long as F<X22_G. When F>X22 or X22>G, the AND gate 29 or inhibit gate 30 sends out an output to operate the latch circuit 32 to send out a defective molding signal W. As described above, according to the present embodiment, when the respective times during which the plunger passes through the preset points Pl, P2, respectively, are not within the ranges between the upper and lower limit values pre-determined for the preset values Pl, P2, respectively, then a defective molding signal W is sent out. Hence, said signal can operate an alarm, or operate a solenoid of the shooter to screen defective products. Namely, in the case the relationship between the travelling distance of the plunger and the time is same as ,~.
. .
1 the curve shown in Fig. 7A, a defective molding signal W is not sent out. In the case of Fig. 7B, 7C or 7H, a defective molding signal W is sent out. According to the present embodiment, the times during which the plunger passes the points Pl, P2, respectively, are indicated by the indicators 8, 11. Hence, the .
indication can be utilized for judging the quality of defect;ve products or the quality of goods products. Further, the upper and lower limit values can be desirably selected ~y.the digi.tal presetters 12 - 15.
Fig. 9 sho~sa circuit for measuring the temperature at a definite point of the mold wi-thin the molding cycle. Said circuit is used together with the circuit s~lown in Fig, 8 for example, so that the judgement of deEect:ive mold:;n~ can ~e per-formed more reliabl~. ~n FicJ. 9, the Eront mold 3~ .is penetra-tingl~ prov:icled w:ith a hole 47 ad.jclcent to a space ~6.
thermoresistance 48 such as a thermister is installed on the bottom of said hole\ 47. 49 is a resistance-voltage converter for converting the resistance value of a temperature measuring resistor 48 into voltage of the resistance-voltage converter 4~
is fed to and held by a sample holding circuit 50. Said sample holding circuit 5~ is adapted to hold a voltage fed from the resistance-voltagè conv~rter 4J, receiving a timi.ng pulse T
from a timing generator 51. The voltage value.held ~y the sample holding circuit 50 ~y the timing pulse Tl from the timing generator 51 is converted to a pulse corresponding in number to the voltage value by a voltage-frequency converter 52. The pulse from the voltage-frequency converter 52 is adapted to ~e fed to a counter 54 through a gate 53 which is opened commensurate to the pulse width of a timing pulse T2 sent out from the timing generator 51. The counter 54 is adapted to be reset hy a timing pulse T3 from the timing generator 51 immediately before the gate g 53 is opened by the timing pulse T2. A pulse fed to the counter 54 through the gate 53 after the counter 54 is reset by the timing pulse T3 is counted ~y the counter 54, and the count number is digitally indicated ~y an indicator 55 The timing generator 51 adapted to repeatedly send out the timing pulses Tl, T2, T3. Only when receiving a pulse signal TS from a pulse generator 56 which will be descrihed hereinafter, the timing generator 51 sends out Tl, T2, T3 each once~ and then f sends out a starting pulse T4 once for a comparator which will ~e described hereinafter. SO is the aforesaid limit switch disposed at a position PO suitable for sending out a signal when the plunger starts from the injection starting position. Said limit switch SO may ~e disposed at a position, for example, shown ~y dot~ed lines in the draw.ing, so that ~he sw:itch can send out a signal when the plunger passes through a po;int a predetcrmine(l distance advanced from the injection starting position. Namely, it can be desirably selected that at what posi-tion in the molding cycl~ the limit switch SO sends out a signal. A si.gnal rom the switch SO is fed to a pulse generating circuit 56 comprising a differentiation circuit and a monostable multivibrator, converted into a pulse signal Ts, and sent to the timing generator 51 through a manual switch 57. 58 and 59 are digita:l. presetters for presetting the upper and :Lower limi.t values o:E the mold tem~
perature, and each comprises a dial type digital switch, for example. 60 and 61 are comparators for comparing the digital values in magnitude. The comparator 60 is adapted to compare the upper limit value of the mold temperature preset hy the digital presetter 58 with the count number of the counter 54 upon receiving a timing pulse T~ from the timing generator 51, and send out a mold off-temperature signal when the count number 34~8 1 of the counter 54 is larger than the upper limit value preset by the digital presetter 58. Additionally, the comparator 61 is adap-ted to compare the count number of the counter 54 with the lower limit value prese-t by the digital presetter 59 upon receiving a timing pulse T4, and send out a mold off-temperature signal when the count number of the counter 54 is less than the lower limit value preset by the digital presetter 59. A mold off-temperature signal sent out from the comparator 60 or 61 is fed to the latch circuit 63 through an OR gate 62 and held 1~ thereby. 64 is a switch similar to said sw:itch 33 for resetting the latch circuit 63.
Description will hereunder be given of the operation of the present embodiment. The temperature of the mold 34 variable during molding cycle is continuously detectecl b~ the temperature measuriny re~,istor ~. The va:Lue~ thus detected :is conv~rted into voltage by the resistance-voltage converter 49, and ~urther, is held by the sample holding circuit 50. The voltage held by the sample holding circuit 50 and commensurate to the mold ` temperature is converted into a pulse by the voltage-frequency converter 52, and fed to the counter 54 through the gate 53 and counted. The count number of the counter 54 is indicated by the indicator 55. Accordingly, if the sw:itch 57 is "OFF", then the mold temperature variable with:in rnolding cycle can be detectecl and digitally indicated by the temperature measuring resi.stor 48 and the indicator 55, respectively. In order to detect -the mold of~-temperature, it lS necessary to preset values in the digital presetters 58, 59 and turn the switch "ON". When the plastici-zation of a resin material is completed, the plunger 42 is advanced to the injection starting position by the hydraulic pressure in a cylinder 44 as indicated by an arrow mark .in the 9LiL~
1 drawing and the ring 45 mounted on a plunger 42 leaves the limit switch SO, whereby said limit switch sends out a signal. This signal causes the pulse generator 56 to generate a pulse Ts.
When said pulse signal TS is fed to the timing circuit 51, said timing circuit 51 sends out timing pulses Tl, T~, T3, T4 each once. Accordingly, the sample holding circuit 50 holds a tem-perature signal at the injection starting time until the succeeding injection starting time, and in corresponding thereto, the counter 54 and the indicator 55 hold and indicate the tem-tO perature until the succeeding injection starting time, respectively.Further, the comparator 60 compares the count number of the counter 54 with the value preset by the digital presetter 58 by use of the timing pulse T~, when the count number of the counter 5~ is less, sends out no output, and, when the count number o~ the counter 5~ is larger than the upper lim:it ~alue preset, sends out an off-temperature signal. Additionally,the comparator 61 compares the count number of the counter 5~ with the lower limit value of the mold temperature preset by the digital presetter 59 by use of the timing signal T~, when the count number of the counter 5~ is larger, sends out no output, and when the count number of the counter 5~ is :Less than the lower limit value, sends out an oEE-temperature si~nal. When either the comparatox 60 or 61 sends out an off-temperature, said signal is fed to a latch circuit 63 through an OR gate 62 and held thereby. The off-temperature signal held by the latch circuit 63 is further sent out to outside, and used as a signal for operating an alarm or the like, for example. According to the present embodiment, if the switch 57 is kept "OFE", then~the mold temperature varying from time to time during molding cycle is digitally indicated by the indicator 55. Additionally, if 1 the switch 57 is kept "ON" and the upper and lower limit values of the mold temperature at the injection starting time are preset by the digital presetters 58 and 59, then the mold temperatures at the injection starting times during the respective molding cycles are indicated~ And at the same time, comparison is made between the mold temperature at the injection starting time in every molding cycle and the upper and lower limit values preset by the digital presetters 58 and 59, an off-temperature signal is sent out when the mold temperature measured at the injection 1~ starting time is not in the range between the upper and lower limit values. In addition, if the limit switch SO is disposed at a new point a predetermined dis-tance advanced from the position PO and the upper and lower limi.t values are preset accordin~ then the mo:ld temperature at the new po.int can be ind.icated, and the detection is made as to whether the mold temperature at the new point is off or not. As described above, the point at which off-temperature is detected in molding cycle may be desirably selected, and may be selected at two or more points. For a signal fed to pulse generator 56, the signal at the time of opening the mold 36 may be used. Further, it is possible to use a thermocouple for measuring the mold temperature.
Claims (8)
1. A plastics injection molding machine including a defective molding detecting device comprising:
a metal mold into which a plastics material is to be fed;
a plunger movable backward and forward in a cylinder communicating with said mold;
first measuring means for measuring the time during which the plunger travels from an initial position to a first point preset within the injection stroke of the plunger;
means for presetting a first upper limit value of the time measured by said first measuring means;
means for presetting a first lower limit value of the time measured by said first measuring means;
means for sending out a defective molding signal when the time measured by said first measuring means deviates from the range between said first upper limit value and said first lower limit value;
second measuring means for measuring the time during which the plunger travels from the initial position to a second point other than the first point preset within the injection stroke of the plunger;
means for presetting a second upper limit value of the time measured by said second measuring means;
means for presetting a second lower limit value of the time measured by said second measuring means;
and means for sending out a defective molding signal when the time measured by said second measuring means deviates from the range between said second upper limit value and the second lower limit value.
a metal mold into which a plastics material is to be fed;
a plunger movable backward and forward in a cylinder communicating with said mold;
first measuring means for measuring the time during which the plunger travels from an initial position to a first point preset within the injection stroke of the plunger;
means for presetting a first upper limit value of the time measured by said first measuring means;
means for presetting a first lower limit value of the time measured by said first measuring means;
means for sending out a defective molding signal when the time measured by said first measuring means deviates from the range between said first upper limit value and said first lower limit value;
second measuring means for measuring the time during which the plunger travels from the initial position to a second point other than the first point preset within the injection stroke of the plunger;
means for presetting a second upper limit value of the time measured by said second measuring means;
means for presetting a second lower limit value of the time measured by said second measuring means;
and means for sending out a defective molding signal when the time measured by said second measuring means deviates from the range between said second upper limit value and the second lower limit value.
2. A plastics injection molding machine including a defective molding detecting device as set forth in claim 1, wherein said initial position of the plunger is the position of the plunger at the commencement of injection.
3. A plastics injection molding machine including a defective molding detecting device as set forth in claim 1, wherein said initial position of the plunger is a position a pre-determined distance advanced from the position of the plunger at the commencement of injection.
4. A plastics injection molding machine including a defective molding detecting device as set forth in claim 1, wherein said first and second measuring means comprise counter circuits, respectively, and said means for presetting the first and second, upper and lower, limit values comprise digital switches, respectively.
5. A plastics injection molding machine including a defective molding detecting device as set forth in claim 1, wherein indicating means are provided for indicating the times measured by said first and second measuring means, respectively.
6. A plastics injection molding machine including a defective molding detecting device as set forth in claim 1, which further comprises:
means for detecting mold temperature at a desired point within the molding cycle;
means for presetting an upper limit value of the mold temperature;
means for presetting a lower limit value of the mold temperature; and
6. A plastics injection molding machine including a defective molding detecting device as set forth in claim 1, which further comprises:
means for detecting mold temperature at a desired point within the molding cycle;
means for presetting an upper limit value of the mold temperature;
means for presetting a lower limit value of the mold temperature; and
Claim 6 continued...
means for sending out a mold temperature off-temperature signal when the mold temperature deviates from the range between said upper and lower limit values of the mold temperature.
means for sending out a mold temperature off-temperature signal when the mold temperature deviates from the range between said upper and lower limit values of the mold temperature.
7. A plastic injection molding machine including a defective molding detecting device as set forth in claim 6, wherein said means for detecting mold temperature is arranged to send out the temperature as a digital value, while said means for presetting an upper limit value of the mold temperature and said means for presetting a lower limit value of the mold temperature are each provided with a digital presetter.
8. A plastics injection molding machine including a defective molding detecting device as set forth in claim 7, wherein means is provided for digitally indicating the temperature detected by said means for detecting mold temperature.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1595977A JPS53101056A (en) | 1977-02-16 | 1977-02-16 | Apparatus for detection of failure of plastics injection molding |
| JP52-15959 | 1977-02-16 | ||
| JP12116577U JPS5451964U (en) | 1977-09-08 | 1977-09-08 | |
| JP52-121165 | 1977-09-08 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1110418A true CA1110418A (en) | 1981-10-13 |
Family
ID=26352191
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA296,055A Expired CA1110418A (en) | 1977-02-16 | 1978-02-02 | Plastic injection molding machine including a defective molding detective device |
Country Status (6)
| Country | Link |
|---|---|
| CA (1) | CA1110418A (en) |
| CH (1) | CH626290A5 (en) |
| DE (1) | DE2803838A1 (en) |
| FR (1) | FR2380865A1 (en) |
| GB (1) | GB1594503A (en) |
| IT (1) | IT1101787B (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3524310C1 (en) * | 1985-04-11 | 1986-06-19 | Wilbrand Prof. Dr.-Ing. 8700 Würzburg Woebcken | Processes and devices for controlled injection molding on different plastic injection molding machines with the same molded part properties and the same masses |
| JP2911560B2 (en) * | 1990-07-24 | 1999-06-23 | 株式会社小松製作所 | Error detection method for injection molding machines |
| CN115972522B (en) * | 2022-12-05 | 2023-11-21 | 上美塑胶（南京）有限公司 | Defective product control system and method of injection molding machine |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE1529787B1 (en) * | 1962-06-01 | 1971-05-13 | Battenfeld Geb | DEVICE FOR MONITORING PROGRAM-CONTROLLED INJECTION, CASTING, PRESSING OR BLOWING MACHINES FOR THE PROCESSING OF PLASTICS |
| US3750134A (en) * | 1971-02-11 | 1973-07-31 | Package Machinery Co | Plastic injection molding machine monitor |
| DE2429874A1 (en) * | 1974-06-21 | 1976-01-08 | Rudolf W Lipp Kunststoffspritz | Automatic control for injection moulding - with control switches operated by screw shaft |
| SE7501748L (en) * | 1975-02-18 | 1976-08-19 | Saab Scania Ab | PROCEDURE FOR THE MANUFACTURE OF PLASTIC GOODS AND APPARATUS FOR PERFORMING THE PROCEDURE |
-
1978
- 1978-01-30 DE DE19782803838 patent/DE2803838A1/en active Pending
- 1978-02-01 CH CH110578A patent/CH626290A5/en not_active IP Right Cessation
- 1978-02-02 CA CA296,055A patent/CA1110418A/en not_active Expired
- 1978-02-15 GB GB6029/78A patent/GB1594503A/en not_active Expired
- 1978-02-15 FR FR7804318A patent/FR2380865A1/en active Granted
- 1978-02-15 IT IT7848051A patent/IT1101787B/en active
Also Published As
| Publication number | Publication date |
|---|---|
| CH626290A5 (en) | 1981-11-13 |
| FR2380865B1 (en) | 1981-09-04 |
| IT7848051A0 (en) | 1978-02-15 |
| DE2803838A1 (en) | 1979-01-04 |
| GB1594503A (en) | 1981-07-30 |
| IT1101787B (en) | 1985-10-07 |
| FR2380865A1 (en) | 1978-09-15 |
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