US3878726A

US3878726A - Device for sampling inspection

Info

Publication number: US3878726A
Application number: US322125A
Authority: US
Inventors: Touru Hamatani
Original assignee: Individual
Current assignee: Individual
Priority date: 1970-06-26
Filing date: 1973-01-09
Publication date: 1975-04-22
Anticipated expiration: 1992-04-22

Abstract

A device for sampling inspection consisting of means for continuously conveying products from a manufacturing machine such as a heading machine; means for repeatedly discharging products in groups; means for holding a sample which represents respective groups of products it belongs to; means for inspecting the sample to judge its quality and transmit an electrical signal corresponding to the results of the inspection; and a member for holding the products discharged from the conveyor means for a given period of time and adapted to further discharge or hold the products according to the electrical signal. By this signal, the operation of the manufacturing machine is halted when an inferior product is produced, thereby enabling the production of inferior products to be minimized. In addition, inferior products can be automatically separated from the satisfactory products already discharged.

Description

ilnited States Patent [1 1 Hamatani Apr. 22, 1975 DEVICE FOR SAMPLING INSPECTION [76] Inventor: Touru Hamatani, No. 2-5-45 lnage.

Chiba. Japan [22] Filed: Jan. 9, 1973 [21] Appl. No.: 322,125

Related U.S. Application Data [63] Continuation-impart of Scr. No. 50744; June 26,

1970, abandoned.

Primary E.\aminer-S. Clement Swisher Attorney, Agent, or FirmStaas & Halsey [57] ABSTRACT A device for sampling inspection consisting of means for continuously conveying products from a manufac turing machine such as a heading machine; means for repeatedly discharging products in groups; means for holding a sample which represents respective groups of products it belongs to; means for inspecting the sample to judge its quality and transmit an electrical signal corresponding to the results of the inspection; and a member for holding the products discharged from the conveyor means for a given period of time and adapted to further discharge or hold the products according to the electrical signal. By this signal, the operation of the manufacturing machine is halted when an inferior product is produced, thereby enabling the production of inferior products to be minimized. In addition, inferior products can be automatically separated from the satisfactory products already discharged.

9 Claims, 10 Drawing Figures mEr-nmnzziws 3.878.726

SEEEU 7 BF 7 FIG. 8a

BACKGROUND AND SUMMARY OF THE INVENTION:

This invention relates to a sampling inspection device for use with a manufacturing machine of relatively high speed and which is adapted to select a sample, estimate the quality of the sample, give an alarm and suspend the operation of its manufacturing machine if the sample is not within predetermined, allowed tolerances, such that inferior products are promptly and surely separated from satisfactory ones already discharged.

When products are manufactured at a relatively high speed, it is difficult from a practical standpoint to inspect all of the materials being produced. Where all products are subjected to an inspection, it is impossible to rapidly detect inferior products, detect possible troubles with the manufacturing machine and immediately halt the operation of the machine for preventing further production of inferior products. Most inferior products of mass production machinery, such as headers, nut formers, punching machines, and molding machines result from damage of a tool, inferiority of a material or misadjustment of the machine, and therefore, are produced successively and not sporadically. Owing to the fact that inferior products are produced successively, a novel system for sampling inspection of products in groups has been devised. First, products supplied form the manufacturing machine are conveyed one after another, and, then, samples are selected and picked out periodically from respective groups of products. Assuming the products produced between a certain sample and a next sample including the latter to be one group, the last product of the group becomes a sample for representing its group. Therefore, when the sample is determined t be satisfactory, all products of the group are deemed to be satisfactory. When the next sample is judged as being inferior, the products of the next group may be a mixture of satisfactory products and inferior products and all the products after the next samples are deemed to be inferior. Thus, the satisfactory products can be surely separated from the inferior ones.

It is an object of the present invention to provide a sampling inspection device which quickly determines the existence of an inferior product by a sampling inspection method and generates an electrical signal when the inferior product is so determined.

It is another object of the present invention to provide a sampling inspection device which is capable of automatically suspending the operation of a manufacturing machine when an inferior product is discovered by the above-mentioned electrical signal thereby enabling the number of inferior products being produced to be minimized.

It is a further object of the present invention to provide a sampling inspection device by which a limited number of inferior products can be automatically separated from satisfactory products already discharged, through a mechanism driven by the electr cal signal.

According to the present invention, the e is provided a sampling inspection device, comprisi ,g a conveyor means, a testing mechanism comprising a sample holder and means to measure the quality of a sample in the holding means, means operatively connected to the conveyor means for alternately discharging a group of products from the conveyor means and feeding the sample which represents the group to the sample holding means, and a member for holding the discharged product thereon until the quality of the sample is determined to be satisfactory.

The invention will be better understood from the following description taken in connection with the accompanying drawings in which:

BRIEF DESCRIPTION OF THE DRAWINGS:

FIG. 1 is a schematic view of the sampling inspection device according to the present invention;

FIG. 2 is a vertical sectional view of one form of the sampling inspection device embodying the present invention;

FIG. 3 is a schematic diagram illustrating the operational relationship between each mechanism of the device shown in FIG. 2;

FIG. 4 is a vertical sectional view of another embodiment of the sampling inspection device according to the present invention;

FIG. 5 is a top plan view of a part of the sampling inspection device illustrated in FIG. 4;

FIG. 6 is an alternative measuring system for use in the sample inspection device of the present invention;

FIG. 7a and 7b are schematic views of a bypass which may be employed between the conveyor and pool member of a preferred embodiment of the sampling inspection device of the present invention; and

FIGS. 8a and 8b are a schematic views of a solenoid coil for operating a movable rail of further embodiment of a sampling inspection device.

DESCRIPTION OF PREFERRED EMBODIMENT:

In FIG. I, there is a schematically illustrated a sampling inspection device comprising a conveyor 1, a guide or path 2, a reservior or pool 3, as sample holder 4 and a measuring device 5. P designates products supplied from a manufacturing machine and travelling on the conveyor 1, and P is a sample held on the sample holding means 4 which is selected from a group of the products to which it belongs so as to represent the group. In other words, the sample P is the last product of the group. P" designates products other than the sample P discharged from the conveyor land held on the pool 3. A predetermined number of products P conveyed in a line and supplied one after another are introduced into and held in a pool member 3 as discharged products p. The sample P belonging to the same group as the discharged products P" is supplied to the sample holding means 4 immediately after the products P are fed to the pool member 3. Products P which follow the sample P are held on the conveyor means 1 for the predetermined period of time required for inspecting the sample P. Meanwhile, the sample P is inspected to check its quality by the measuring means 5. If the sample is found to be satisfactory it is removed from the holding means 4, and the products P" held in the pool member 3 are discharged. This sequence is continually repeated throughout the operation of the machine. If the sample P is judged to be outside of allowable tolerances, an electrical signal is generated not to discharge the product P from the pool member 3 but to separate them from the process or the products already discharged and determined to be satisfactory. Additionally, an alarm will be given or the operation of the manufacturing machine will be halted.

A detailed description of each component of the above-mentioned device now follows.

The conveyor 1 is adapted not only to successively convey the products P in a line thereon but also to temporarily hold the products P supplied from the manufacturing machine during the time when the path means 2 is closed and the inspection of the samples P is being carried out. The conveyor means 1 is, in practice, designed according to the size and shape of the product to be inspected as well as the measuring area and type of inspection. Generally, a vibrating conveyor of a U-shape cross section is the most suitable for the conveyor means 1. The length of the conveyor is determined by the speed of the manufacturing machine as well as the inspection cycle of the measuring mechanism. The conveyor means 1 may, of course, be formed as a T-shape in section if the shape of the products so requires. A belt-conveyor, a bucket-conveyor or other suitable conveyor may be employed according to necessity. The path means 2 is adapted to introduce into a pool member 3 the predetermined number of products that are supplied from the manufacturing machine before the sample. The path means 2 may be constructed in any one of the following ways. The conveyor means 1 may have an end portion serving as a path means 2 which is periodically opened or closed in synchronism with an inspection cycle, stated illustratively, it is closed when the inspection of the sample is being carried out and then opened to let the following group of products be discharged to the pool member 3. Alternatively, the path means 2 and the sample holding means 4 are provided on one member which is adapted to rotate, by a predetermined angle, to alternately effect the discharge of the products and the sampling, in synchronism with an inspection cycle. The path means 2 may also be structured alternatively so that the conveyor means 1 is connected to the sample holding means and the path means 2 is separately provided and synchronized with an inspection cycle. A suitable construction may be selected from the above-mentioned structures depending on the size and shape of the products, as well as measuring arean and the kind of sampling inspection, and the speed of manufacture and sampling inspection among other factors. The pool member 3 has a door adapted to operate in synchronism with the inspection cycle and keep closed by the action of a relay provided in the measuring means 5 which generates an electrical signal for controlling the operation of the door when the same is found to be inferior. The pool member 3 having the door, as shown in FIG. 1, may be replaced by a conveyor on which the products discharged from the conveyor means 1 and to be conveyed to the following process are held. In this case, the conveyor is adapted to be suspended when the sample is judged as being inferior and the products discharged to the conveyor are held. Such a conveyor is placed between the device for sampling inspection and the following process for further treatment of the products. Some proper bypass may be additionally empolyed between the conveyor means the pool member. As shown in FIGS. 7a and 712, products supplied through a receiving plate 6 from a heading machine travel along the conveyor means 13. At an end portion of the conveyor means 13 are formed a portion 14 and a bypass portion 24. The products supplied from the heading machine are introduced partially to the bypass portion 14 to be discharged on a pool member 3. The portion 14 faces a sample holding table 4 which is adapted to be rotated counterclockwise by The table 4 has an increased diameter portion 47 and a decreased diameter portion 46. A sample holding groove 45 is provided in the increased diameter portion 47. Accordingly, when the table 4 is stopped in the position wherein the groove 45 faces the portion 14, one of the products on the portion is supplied as a sample to the groove 45. After the table 4 is further rotated by 180", the sample is positioned in the measuring area 48 and the decreased diameter portion 46 faces the portion 14, letting the products thereon be discharged onto the pool member 3. An expelling means 73 is adapted to remove the sample according to the rotation of the table 4 after the inspection thereof. Above the measuring area there is provided ,a testing mechanism which effects inspection of the sample and transmits an electrical according to the result of the inspection. The pool member 3 is controlled by the electrical signal from the testingmechanism and is adapted to be suspended when the sample is determined to be inferior. The products discharged on the pool members are transmitted to the next process when the sample is judged as satisfactory. The time when the discharge products are conveyed on the pool member 3 is determined to be more than a time required between supply of the sample and transmission of an electrical signal after inspection of the sample plus inspection cycle. The sample holding means 4 a sample P under the center of the measuring means 5. The measuring means 5 comprises a mechanism for converting the quality of the sample into an amount of mechanical displacement of a gauge (or hydraulic or electrical value) and a circuit for reading the thus converted value to judge the quality of the sample. The measuring means 5 is, in practice, designed according to a shape to be inspected and the accuracy required for the inspection. If not so high accuracy is required, the gauge is brought into engagement with the sample and the amount of the displacement of the gauge may be directly transmitted to an electric contact to obtain only an ON-OFF signal. While, if high accuracy and reliability is required, a differential transformer or a converting means of an electrostatic capacity may be connected to the gauge and a judging circuit.

Embodiments of the present device for sampling inspection employed with a heading machine for crossholed screw, and used for the measurement of a depth of engagement of a cross-pointed gauge with the crosshole (hereinafter referred to as a Q value Japan Industial Standards B-lOl 2), will be described by way of example. The engaging strength of a cross-hole (refer to Japan Industrial Standards 8-1012) can, of course, be measured by using an adequate gauge.

EXAMPLE 1 Referring now to FIGS. 2 and 3, there are respectively illustrated a device for detecting a Q value of a cross-recessed head (including a wood screw) and an operational relationship between each mechanism of the device.

A receiving plate 6 and a pair of parallel rails 11 forming a conveyor shown in FIG. 2, are adapted to be vibrated by a vibrator 12. The distance between the parallel rails 11 is slightly wider than the diameter of a screw stem and wide enough to readily convey the screw. One of the parallel rails is cut off at its end portion to form a movable rail portion 21 which serves as a path. The movable rail 21 is normally aligned with one of the parallel rails, forming a conveying path in cooperation with the other of the parallel rails as shown in FIG. 8a. When a solenoid coil 22 is energized by a limit switch 81 which is controlled by a timing cam 83, the movable rail portion 21 moves outwardly as shown in FIG. 8b letting products conveyed on the parallel rails 1 1 be discharged onto a pool member 31. The cam 83 is mounted on a shaft driven by a geared motor 43. On the shaft are mounted another timing cam 84 for controlling another limit switch 82 and an eccentric cam 44 for controlling periodical up-and-down move ment of a sample holding means 41.

The belt conveyor 31 functions not only as a pool member but also as a material supplier for the following process, for example a threading machine. The sample holding means 41 is a shaft of a horseshoe shape in section and has an opening 42 of the same shape which faces the parallel rails 11. The sample holding means 41 is adapted to reciprocate up and down following an eccentric cam 44 on the shaft connected to the geared motor 43 and the upper surface of the receiving table is aligned with the end of the parallel rails when the means 41 is lowered to the lowermost point. At this instance, a sample is supplied from the parallel rails 11 to the sample holding table 41. As shown in FIG. 3, the limit switch 81 is turned on by the timing cam 83 in the descending course of the sample holding means 41. Upon this turning on of the limit switch 81, the solenoid coil 22 and another solenoid coil 71 are energized. The limit switch 82 is turned on by the timing cam 84 at the uppermost position of the sample holding means 41. An expelling means 7 moves horizontally by the energization of the solenoid coil 71 due to the turning-on of the cam 81 during the descending course of the sample holding means 41 and removes the sample retained in the samples folding means 41. A frame of a measuring means is secured to a main body of the device by a fixing means 52. The sample is pressed against the measuring means and the inspection of the sample P is effected at the time when the receiving table 41 is elevated to the uppermost point. Within the frame 51 of the measuring means, a gauge shaft 53 with a cross point is supported by a gauge sleeve 54 at its lower portion and by a bearing 55 at its upper portion. A rotary drum 57 is fixed to the mid portion of the gauge shaft 53 and a driving drum 58 is provided in contact with the periphery of the rotary drum 57 to rotate the gauge shaft 53 by a geared motor 59. The gauge sleeve 54 is supported by a bearing 510 and urged downwardly by a coil spring 511. An annular -Q-measuring electrode 512 is connected to the gauge sleeve 54 through an insulator 513. The Q-measuring electrode 512 and the rotary drum 57 are so sized that the former may surround but not contact the electrode. Accordingly, the electrostatic capacity between the Q-measuring electrode 512 and the rotary drum 57 varies with relative axial displacement of the gauge shaft 53 and the gauge sleeve 54, which corresponds to the Q value of the sample. An electronic circuit 514 provided separately reads, at the top dead point of the receiving table 41, the electrostatic capacity between the rotary'drum 57 and the Q-measuring electrode 512, thereby judging the quality of the sample and energizes a Q-judging relay 515 to operate according to the judgement. A

limit switch 82 is operated as mentioned before, at the upper dead point of the receiving table 41 to determine an operational time of Q-judging relay 515. The Q- judging relay 515 is turned off when the sample is inferior, stopping the operation of the conveyor 31 and holding the group of the products to which the sample belongs, discharged through the path means 21. Furthermore, upon turning -off of the relay, the operation of the manufacturing machine is suspended. The length of the conveyor and the speed of the operation thereof are determined to hold the products discharged on the conveyor until the sample, representative of the products, is determined to be satisfactory.

The measuring means may alternatively comprise, as shown in FIG. 6, a gauge shaft 63 having a crosspointed gauge 61 for measuring a Q value (hereinbelow referred to as a Q gauge) and a differential transformer core 62, and a lever 64 connected to the gauge shaft 63. The Q gauge 61 is inserted in a gauge sleeve 65 and the gauge shaft 63 is supported by a bearing 68. To the gauge sleeve 65 are connected a differential transformer coil 66 and a hollow coil core 67. The periphery of the gauge sleeve 65 is supported by a slide bearing 69. The coil core 67 is so constructed that it slides on the gauge shaft 63 and is normally urged downwardly by a compression coil spring 610. When a sample is inspected, pressure is applied to the gauge sleeve 65 to move the gauge sleeve upward together with the coil core 67 thereby measuring a Q value. On the other hand, a pin 612 is fixed at an eccentric portion of a disc 611 which is rotated in one direction by a proper prime mover, one end of a tension coil spring 613 being connected to a lever 64 and the other end of said tension coil spring 613 being fixed to a frame so as to urge the lever 64 to contact the pin 612, thereby to reciprocatingly pivot the gauge shaft 63, the differential transformer core 62 and the Q gauge 61 according to the rotation of the disc 611. The angle of the reciprocating pivotal movement is preferably as small as possible so far as the Q gauge can securely engage with a crosshole. It normally ranges from 20 to 40. The force of the tension coil spring 613 is preferably large enough to follow the eccentric movement of the pin 612 when no pressure is applied and small enough to race the disc 611 and the pin 612 when a pressure is applied.

EXAMPLE 2 Another embodiment of the present sampling inspection device for inspecting Q of a cross-holed screw is shown in FIG. 4. This embodiment differs from that of Example 1, as follows.

A path means is provided in a sample holding table 91 which is rotated, by a predetermined angle, synchronizing with an inspection cycle to effect the discharging of a group of products and sampling of a representative thereof alternately. This structure is suitable when a short inspection cycle is desired. According to Example 2, a pair of slots, namely, a discharging slot 23 and a receiving groove 43, are provided on the periphery of the table 91. The sample receiving table 91 may be provided with two or more pairs of slots so that two or more inspections can be effected for each revolution of the table thereby shortening the inspection cycle.

The table 91 for holding a sample does not shift up and down. The measuring means 5, instead, descends to inspect the slot headed of the sample. However, such a structure as disclosed in Example 1, in which the measuring means is fixed and the table with a sample is moved up or down, can alternatively be employed. A door 32 provided under the discharging path may be opened or closed to function as a pool member for the products, while a sample, namely, a representative of one group of the products, is being inspected. A conveyor may, of course, be employed for the pool member as disclosed in Example 1. Finally, an expelling means 72 is fixed to the frame and adapted to eject the sample.

In operation, a receiving plate 6 and a pair of rails 11 functioning as a conveying path are vibrated by a vibrator 12. The table 91 is adapted to rest every one-third rotation thereof by means of a motor 92 and a camclutch 93. On the periphery of the table 91, are provided, as shown in FIG. 5, a sample holding groove 43 and a path slot 23, respectively, to form a sample holding means and a path means. When the table 91 is stopped in a position where the path slot 23 faces the end of the parallel rails, the products on the conveyor are discharged through the slot. The amount of discharge is determined according to the amount of supply by the conveyor per unit time and suspended time of rotation of the table 91. When the table 91 is then stopped after one-third rotation, the holding groove 43 meets the parallel rails 11 and a sample is fed to the holding groove 43. When the table 91 is further rotated by one-third rotation, the sample retained in the holding groove 43 shifts under the axial center of the measuring means 5. At this time, the ends of the parallel rails are closed by the periphery of the table 91. While the table 91 rests in this state, the measuring means shifts down by means of a motor 92, a cam 94 and a lever 95 inspect and estimate a cross-hole of the sample. If the Q value of the cross-hole is judged as being normal, the table 91 further rotates by one-third to return to its original position to let the following groups of products be discharged. Simultaneously, the pool member 32 is opened by an energized solenoid coil 33. The expelling means 72 is fixed to the frame and is adapted to remove a sample when the inspected and estimated sample is touched by the expelling means as the table rotates. If the Q value of the cross-hole is judged as being outside of allowable tolerances, the motor will be stopped and the pool member will continue to keep the products by means of a Q-judging relay attached to the measuring means 5 and further an alarm will be given or the operation of manufacturing machine will be suspended. In such a case, the products already supplied to the pool members are regarded as inferior and separated from the normal products which are already discharged from the pool member. The measuring means 5 of this Example is identical with that of Example 1. Though these means are adapted to perform a Q-cheeking of the cross-hole in these Examples, they also may effect inspection of the engaging strength of the cross-hole by employing a gauge suitable for the purpose and an appropriate detecting mechanism necessary therefor. In case a sample is not selected so as to be the last product of the group to which the sample belongs, a

pool member

3 or 32 as shown in FIG. 1 or FIG. 4 is constructed to have another

pool memmber

3 or 32, respectively, and a pool member 31 as shown in FIG. 2 is structured to have a length sufficient to hold two groups of products thereon.

While the particular device for sampling inspection herein shown and disclosed in detail is fully capable of attaining the objects and providing the advantages hereinbefore stated, it is to be understood that it is merely illustrative of the presently preferred embodiments of the invention and that changes, omissions, additions, substitutions and/or other modifications may be made without departing from the scope of the invention as defined in the appended claims.

I claim:

1. A device for sampling inspection, comprising: conveyor means, a testing mechanism provided with sample holding means and means to measure a property of a sample, said sample holding means being provided with a sample receiving member adapted for reciprocating up and down motion, an eccentric cam attached to said member to'cause said up and down movement, and means for expelling the sample from said receiving member, said receiving member being aligned to receive a sample at the bottom of the cycle and positioned to permit measurement of a property by said means to measure at the top of the cycle, and means adapted to be operated in association with said conveyor means for alternatively discharging a group of products from said conveyor means and feeding a sample of said product to said sample holding means; and a pool member positioned to accept the products discharged from said conveyor means and hold the products thereon until the property of the sample is determined to be satisfactory.

2. A device as in claim 1, wherein said testing mechanism comprises a gauge carried by a pivotable shaft at its lower end and an electrical difference detecting means consisting of an inner member which is positioned on the shaft and an outer member which is positioned around said inner member and adapted to move up and down, a compression spring for moving said outer member, said outer member being provided at its lower end with a gauge sleeve. I

3. A device as in claim 1 wherein said testing mechanism further comprises a limit switch which is operated as the sample receiving member descends to energize a solenoid coil; and a limit switch which is operated when the sample receiving member is at the top of its cycle to determine an operating time of a judging relay, these limit switches being operated by a timing cam mounted on the same shaft as the eccentric cam.

4. A device as in claim 1, wherein said sample holding means and said sample discharging means are respectively a groove and a slot provided on the periphery of a table, said table being adapted to rotate and rest after rotation of a predetermined angle synchronized with an inspecting cycle to sequentially effect a discharging, sampling and inspecting.

5. A system for inspecting a plurality of products, comprising:

inspection station means; conveyor means for transporting a predetermined number of the products defining a group to the vicinity of said inspection station means;

means selecting the last one of said number of said products of said group as a sample and transporting same to said inspection station means for inspection;

pool means;

means delivering said products of said group other than said sample that has been selected to said pool means; and

means releasing said products of said group other than said sample from said pool means only after said inspection station means has approved said sample that has been selected.

6. A system for inspecting as in claim 5, wherein said means releasing remainder of said products of said group other than said samples from said pool means only after said inspection station means has approved said one of said products that has been selected includes means for signalling said pool means so as to release said products of said group other than 'said sample, and means regulating the time said products of said group other than said sample remain in said pool means to be greater than the time between the supply of said sample to said inspection station means and the completion of the inspection of said sample at said inspection station means.

7. A system for inspecting a plurality of products as in claim 6, wherein said inspection station means comprises a gauge carried by a pivotable shaft at its lower end and an electrical difference detecting means consisting of an inner member which is positioned on the shaft and an outer member which is positioned around said inner member and adapted to move up and down,

a compression spring for moving said outer member,

said outer member being provided at its lower end with a gauge sleeve.

8. A system for inspecting a plurality of products as in claim 7, wherein said inspection station means further comprises a sample receiving member adapted for reciprocating up and down motion, a limit switch which is operated as said sample receiving member descends to energize a solenoid coil; and a limit switch which is operated when the sample receiving member is at the top of its cycle to determine an operating time of a judgement relay, and eccentric cam attached to said sample receiving member to cause the up and down movement, said limit switches being operated by a timing cam mounted on the same shaft as said eccentric cam.

9. A system for inspecting a plurality of products as in clim 6, wherein said means selecting the last one of said number of said products of said group as a sample and transporting same to said inspection station means for inspection and said means delivering said products of said group other than said sample that has been selected to said pool means are respectively a groove and a slot provided on the periphery of a table, said table being adapted to rotate and rest after rotation of a predetermined angle synchronized with an inspecting cycle to sequentially effect discharging, sampling and inspecting.

Claims

1. A device for sampling inspection, comprising: conveyor means, a testing mechanism provided with sample holding means and means to measure a property of a sample, said sample holding means being provided with a sample receiving member adapted for reciprocating up and down motion, an eccentric cam attached to said member to cause said up and down movement, and means for expelling the sample from said receiving member, said receiving member being aligned to receive a sample at the bottom of the cycle and positioned to permit measurement of a property by said means to measure at the top of the cycle, and means adapted to be operated in association with said conveyor means for alternatively discharging a group of products from said conveyor means and feeding a sample of said product to said sample holding means; and a pool member positioned to accept the products discharged from said conveyor means and hold the products thereon until the property of the sample is determined to be satisfactory.

2. A device as in claim 1, wherein said testing mechanism comprises a gauge carried by a pivotable shaft at its lower end and an electrical difference detecting means consisting of an inner member which is positioned on the shaft and an outer member which is positioned around said inner member and adapted to move up and down, a compression spring for moving said outer member, said outer member being provided at its lower end with a gauge sleeve.

5. A system for inspecting a plurality of products, comprising: inspection station means; conveyor means for transporting a predetermined number of the products defining a group to the vicinity of said inspection station means; means selecting the last one of said number of said products of said group as a sample and transporting same to said inspection station means for inspection; pool means; means delivering said products of said group other than said sample that has been selected to said pool means; and means releasing said products of said group other than said sample from said pool means only after said inspection station means has approved said sample that has been selected.

6. A system for inspecting as in claim 5, wherein said means releasing remainder of said products of said group other than said samples from said pool means only after said inspection station means has approved said one of said products that has been selected includes means for signalling said pool means so as to release said products of said group other than said sample, and means regulating the time said products of said group other than said sample remain in said pool means to be greater than the time between the supply of said sample to said inspection station means and the completion of the inspection of said sample at said inspection station means.

7. A system for inspecting a plurality of products as in claim 6, wherein said inspection station means comprises a gauge carried by a pivotable shaft at its lower end and an electrical difference detecting means consisting of an inner member which is positioned on the shaft and an outer member which is positioned around said inner member and adapted to move up and down, a compression spring for moving said outer member, said outer member being provided at its lower end with a gauge sleeve.