US3729267A - Mechanical pencil - Google Patents

Mechanical pencil Download PDF

Info

Publication number
US3729267A
US3729267A US00164271A US16427171A US3729267A US 3729267 A US3729267 A US 3729267A US 00164271 A US00164271 A US 00164271A US 16427171 A US16427171 A US 16427171A US 3729267 A US3729267 A US 3729267A
Authority
US
United States
Prior art keywords
barrel
cartridge
chuck
sleeve
disposed
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 - Lifetime
Application number
US00164271A
Other languages
English (en)
Inventor
J Hori
K Nishiyama
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Sailor Pen Co Ltd
SAILOR PEN CO
Original Assignee
Sailor Pen Co Ltd
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Sailor Pen Co Ltd filed Critical Sailor Pen Co Ltd
Application granted granted Critical
Publication of US3729267A publication Critical patent/US3729267A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B43—WRITING OR DRAWING IMPLEMENTS; BUREAU ACCESSORIES
    • B43K—IMPLEMENTS FOR WRITING OR DRAWING
    • B43K21/00—Propelling pencils
    • B43K21/02—Writing-core feeding mechanisms
    • B43K21/16—Writing-core feeding mechanisms with stepwise feed of writing-cores

Definitions

  • a mechanical pencil comprising a cartridge slidably inserted into the lower part of a barrel and containing [30] Foreign Application Priority Data May 1 1,
  • This invention relates to a mechanical pencil and more particularly to a mechanical pencil wherein the insertion and withdrawal of a piece of pencil lead can be easily effected simply by depressing a push button.
  • Some of the conventional mechanical or propelling pencils are so constructed that the lower end ofa barrel contains a chuck which normally holds a piece of pencil lead and the depression ofa push button disposed at the upper end of the barrel causes the pencil lead to project from the tip end of a pencil body for a required length.
  • this type of mechanical pencil has the drawback that since the pencil lead can not be allowed to project appreciably from the tip end ofa pencil body to prevent the possible breakage of the pencil lead, the push button has to be often depressed during writing to draw out the pencil lead.
  • the lead should have an additional or unnecessary length at least to match the length of a bore penetrating the tip member of the pencil body plus that ofa chuck including its pinch portion in order to be securely held by the chuck. Therefore, when the lead is consumed until there is only left said additional length, it can no longer be used in writing, but has to be replaced by a fresh piece. This means that said additional length of the pencil lead is simply wasted.
  • Another object of the invention is to provide a mechanical pencil which enables substantially all the pencil lead to be used, offering great saving on its consumption.
  • Still another object of the invention is to provide a mechanical pencil which enables pencil lead alone or together with a cartridge to be very easily replaced.
  • a mechanical pencil according to this invention has a pencil lead cartridge coaxially inserted into the lower part of a barrel.
  • the cartridge frictionally engages a bushing elastically and forcefully holding the periphery of said cartridge.
  • Into the cartridge is slidably inserted a piece of pencil lead coaxially in the lengthwise direction.
  • a chuck coaxially with the cartridge.
  • the chuck is so designed as to move lengthwise by the operation of a push button fitted at the upper end of the barrel.
  • a sleeve Substantially at the middle part of the barrel is received a sleeve. Between the upper end of the sleeve and the lower end of the push button is stretched a compression spring to normally urge the chuck upward.
  • the shoulders of the chuck are pressed against an abutment provided in the chuck sleeve by the action of the compression spring so as to keep the chuck closed.
  • the chuck is brought downward against the force of the compression spring and opened due to disengagement of the shoulders from the abutment.
  • the chuck is penetrated coaxially with the barrel by a needle member narrower than or as narrow as the pencil lead and at least as long as the cartridge. The needle member is firmly held by the chuck when it is closed and moves lengthwise of the barrel when the chuck is opened.
  • FIG. 1 is a cross-sectional view of an embodiment of a mechanical pencil according to the present invention
  • FIG. 2 is an enlarged partial view of the principle portion of FIG. I.
  • FIG. 3 is a cross-sectional view of another embodiment of a mechanical pencil of the present invention.
  • the barrel of a mechanical pencil according to the present invention is generally designated by numeral 1.
  • the barrel comprises a hollow cylindrical upper barrel member 2 and a cylindrical lower barrel member 3 having a through hole 3a provided therein.
  • a chuck sleeve 4 has male screw threads formed along its periphery. With these male screw threads are engaged female screw threads formed in the lower inner walls of the upper barrel member 2 and those of the lower barrel member 3. These barrel members 2 and 3 may be made into a substantially integral barrel 1.
  • the lower barrel member 3 preferably consists of transparent plastic material.
  • a metallic tip 5 of the same type as that used in the conventional mechanical pencil is screwed to the end portion of the lower barrel member 3 .
  • the tip 5 is perforated with a through hole 5a coaxial with the through hole 3a in the lower barrel member 3 and having the same diameter as the latter hole 3a.
  • Numeral 6 denotes a tubular cartridge of plastic material having a piece of pencil lead 7 inserted into its through hole 6a, said cartridge 6 being adapted, for example, to be thrown away after use.
  • This cartridge 6 is slidably inserted lengthwise of the aforesaid through holes 3a and 5a and is fitted at the front end with a metallic tubular piece 6b.
  • the cartridge 6 should preferably be formed of plastic material which is sufficiently transparent to see how much of the pencil lead contained therein has been consumed, and, as described above, is adapted to be thrown away after use.
  • Numeral 7a is a pencil point.
  • annular bushing or a brake member 8 for holding the cartridge 6 loosely as well as elastically so as to prevent the cartridge 6 from projecting from the tip 5, so long as the mechanical pencil is only subjected to slight shaking or impact.
  • the chuck sleeve 4 is bored with a through hole 40 coaxial with the barrel 1.
  • This through hole 4a has a relatively larger diameter in the section extending from tion of said hole 4a define a conically tapered abutment 4b whose radius is progressively reduced toward the top.
  • Numeral 9 is a chuck having an inverted funnel shape.
  • the large diameter portion of the lower end is divided in cross section into, for example, three equal parts which constitute jaws 9a elastically expansible to the outside.
  • the conically tapered shoulders 9b forming the upper end portion of the jaws 9a are made engageable with the chuck abutment 4b.
  • the stock 90 of the chuck extends upward.
  • the chuck 9 is perforated with a through hole 9d coaxial with the barrel I. Said through hole 9d has a sufficient diameter for a needle member 13 to pass therethrough without any obstruction when the chuck is opened.
  • a guide tube 10 Into the upper barrel member 2 is fitted a guide tube 10, to the upper end of which there is screwed a push button 11 extending upward from the upper end of the barrel 1. To the lower end of tube 10 is fixed 'the upper portion of the chuck stock 9c. Between the lower end of the push button 11 and the upper end face of the sleeve 4 is stretched a compression spring 12 surrounding the guide tube 10 so as to urge the chuck 9 upward through the guide tube 10.
  • the needle member 13 is received in the guide tube 10.
  • the needle member 13 moves lengthwise of the barrel 1 and, when the push button 11 is released, is lifted by the force of the spring 12, causing the shoulders 9b of the chuck 9 to be pressed against the chuck abutment 4b and in consequence thejaws 90 thereof to be closed.
  • the needle member 13 is firmly held by the jaws 9a.
  • the needle member 13 has a slightly smaller diameter than or the same diameter as that of the through hole 6a of the cartridge 6.
  • the upper end of the needle member 13 forms a stop or a, stop member 13a having a larger diameter than that of the upper opening of the through hole 9a of the chuck 9 so as not to be drawn out of the guide tube 10.
  • the needle member 13 has such a length as it projects just slightly from the furthest end of the tip 5 when said needle member 13 is brought to its lowest position.
  • the push button 11, as well as the guide tube 10 and chuck 9, is brought back to the original position by the biasing force of the compression spring 12. Since, at this time, the shoulders 9b of the chuck 9 are pressed against the abutment 4b, the jaws 9a are closed to hold the needle member 13 again. However, the cartridge 6 is still in a state projecting from the tip 5 and the lower end of the needle member 13 remains pressed against the upper end of the pencil lead 7.
  • the cartridge 6 When, under such condition, the furthest end of the tubular piece 6b of the cartridge 6 is made to touch a sheet of paper or similar material, then the cartridge 6 is lifted just slightly by contact pressure to cause the pencil point 7a to appear to the outside as illustrated in FIG. 2. Since the cartridge 6 is frictionally engaged with the bushing 8, it is prevented during writing from projecting from the tip 5 with ease or falling off the pencil body. Moreover, the upper end of the pencil lead 7 contacts the needle member 13 firmly held by the chuck 9, the pencil lead 7 is prevented from being drawn into the lower barrel member 3 even when it is subjected to the aforesaid contact pressure or writing pressure.
  • this invention does not cause the pencil lead 7 to be directly held by the chuck 9, but to be delivered in contact with the needle member 13 upon depression of the push'button l 1, thereby enabling the pencil lead 7 to be used to the end.
  • depression of the push button 1 l disengages the needle member 13 from the chuck 9.
  • the pencil point 7a and tubular piece 6b are pushed upward by pressure resulting from the contact of the pencil body with writing material, then the pencil lead 7 is drawn into the-lower barrel member 3 together with the cartridge 6 while pushing the needle member 13.
  • the chuck 9 again holds the needle member 13, the cartridge 6 and pencil lead 7 remain retracted into the lower barrel member 3.
  • the cartridge 6 and lower barrel member 3 are made of transparent material, the condition of the pencil lead received in the lower barrel member 3 can be observed from the outside, providing warning that exhaustion of the lead is impending.
  • FIG. 3 illustrates a mechanical pencil according to another embodiment of this invention.
  • the parts of FIG. 3 corresponding to those of FIGS. 1 and 2 bear reference numerals consisting of the original numerals to which there has been added a number of 100.
  • the parts of FIG. 3 have the same shape and function as those of the preceding embodiment of FIGS. 1 and 2.
  • the barrel 101 of the mechanical pencil comprises an upper barrel member 102 and a lower barrel member 103 threadably engaged at the upper, portion with the lower portion-of the upper barrel member.
  • Said upper barrel member 102 consists of first, second and third hollow cylindrical portions 102a, 1021; and 102C.
  • the second cylindrical portion 102b is disposed substantially at the middle part of the barrel 101 slightly above the chuck stock 109a, and has cylindrical bosses 102d, l02e of small diameter formed at the upper and lower ends.
  • the upper boss 102d is securely fitted into the lower end portion of the first cylindrical portion 102a and the lower boss 102e into the upper end portion of the third cylindrical portion 1020.
  • these first, second and third cylindrical portions 102a, l02b and 1020 are substantially formed into an integral body.
  • the second cylindrical portion 102b has a through hole for allowing a cylindrical guide tube 110 to slide therethrough.
  • FIG. 3 includes an axially movable chuck sleeve I17 surrounding the stock 1090 of the chuck 109 instead of the stationary sleeve 4 used in the embodiment of FIGS. 1 and 2.
  • Said chuck sleeve 117 has a coaxial through hole provided at the lower end with an abutment mating the shoulders 10911 of the chuck 109.
  • the chuck 109 is normally closed to hold the needle member 113 which has passed through the hole 109d of the chuck 109.
  • Numeral 115 is a hollow cylindrical abutment member with a blind lower end 115a screwed to the lower end of the third cylindrical portion 102c.
  • the jaws 109a of the chuck 109 are brought into said hollow cylindrical abutment member 115.
  • a ring guide member 116 perforated with a coaxial through hole to guide the needle member 113 for alignment with the pencil lead 107.
  • the blind end 115a is bored with an aperture 115b slidably to receive the cartridge 106.
  • the cartridge 106 is also slidably received in a metallic tubular piece 106b which is disposed in a hole 105a bored through a tip 105 connected to the lower end of the lower barrel member 103. 1
  • the chuck 109 is opened by being disengaged from the ring sleeve 117, causing, as in the embodiment of FIGS. 1 and 2, the cartridge 106 to be drawn out of the forward end of the tip 105.
  • depression of the push button 111 causes the needle member 113 to descend on to the upper end of the pencil lead 107 if they are separated from each other, and release of said push button 111 causes the needle member 113 to obstruct the upward movement of the pencil lead 107.
  • the push button 111 is depressed again, the chuck 109 is brought downward.
  • the lower end of the chuck sleeve 117, together with the chuck 109, is let down until it contacts the upper end of the hollow cylindrical abutment member 115 with said sleeve 117 engaged with the chuck shoulders 10% by the outward acting elastic force of the chuck 109.
  • the push button 111 still continues to be depressed after said contact, the chuck 109 is opened for the first time.
  • the needle member 113 falls in a state held by the chuck 109 to an extent equal to the distance through which the chuck sleeve 117 travels from its position abutting against the second cylindrical portion 102k to its position contacting said hollow cylindrical member 115, thereby causing the point 107a of the pencil lead 107 to project from the tip to the same extent.
  • the chuck 109 When, upon release of the push button 111, the chuck 109, together with the chuck sleeve 117 is lifted by the spring 112 to be pressed against said sleeve 117, then the chuck is closed by having its shoulders 109b immovably engaged with the tapered lower end portion of the sleeve 117, causing the needle member 113 to be held by the chuck 109 thus closed. Since, however, the chuck 109 is not closed until the chuck sleeve 117 is brought back to its original position from the point at which it abuts against the hollow cylindrical member 115, the needle member 113 remains urged downward. Therefore, each time the push button 111 is depressed after the second time, the pencil lead 107 is delivered to an extent equal to said depression, permitting an inching operation as in'the conventional mechanical pencil.
  • the upper end of the needle member 113 is provided with a colored stop 113a having a larger diameter than that of the central through hole of the chuck stock 1090, then it is possible easily to find out from the outside the full or approximate exhaustion of the pencil lead 107 when said colored stop 113a is brought to the second cylindrical portion 102b.
  • a brake member indicated by 108 of FIG. 3 may consist of a large diameter section and a small diameter section split into a plurality of equal divisions along the periphery so as to be pressed against the cartridge 106.
  • a mechanical pencil comprising:
  • a brake member disposed in the lower portion of said barrel and acting to frictionally engage and hold said barrel and acting to frictionally engage and hold said cartridge when said cartridge is inserted thereinto;
  • a lengthwise movable needle member coaxially disposed in said barrel and engageable at the lower end thereof with the upper end of said pencil lead to prevent the upward movement of said lead;
  • depressible means slidably mounted at the upper end of said barrel
  • chucking means formed substantially integral with said depressible means to normally hold in position said needle member which penetrates through said chucking means and causes the cartridge to project from the lower end of the barrel upon depression of said depressible means;
  • a sleeve located in said barrel to normally close said chucking means and having a through hole therein through which said needle member passes, said sleeve being disengaged from said chucking means to open said chucking means upon depression of said depressible means;
  • urging means disposed between said sleeve and depressible means to urge said chucking means upward.
  • the mechanical pencil according to claim 1 wherein said sleeve has a tapered abutment in the through hole, and said chucking means is provided with jaws equally arranged in the peripheral direction, each jaw having a tapered shoulder engageable with said abutment to close said chucking means for holding said needle member and allowing the cartridge to project from the tip upon depression ofsaid depressible means 3.
  • said barrel comprises a substantially cylindrical upper barrel member connected at the lower portion with the upper part of the sleeve, containing the chucking means as well as the needle means and slidably supporting said depressible means at the upper end thereof, and a substantially cylindrical lower barrel member having a coaxial through hole for receiving said cartridge therein.
  • the mechanical pencil according to claim 1 further comprising a ring member under the chucking means, said ring member having a through hole therein to guide the needle member for alignment with the pencil lead in the cartridge inserted into the barrel.
  • a mechanical pencil comprising:
  • a barrel comprised of a substantially cylindrical hollow upper barrel member and a substantially cylindrical transparent hollow barrel member;
  • a transparent tubular cartridge slidably and coaxially inserted into both the lower barrel member and said tip and having a piece of pencil lead coaxially passing therethrough;
  • an elastic ring shaped brake member disposed in the lower part of said lower barrel member to frictionally engage and hold said cartridge inserted thereinto;
  • a churck sleeve connecting said upper barrel member with said lower barrel member, said chuck sleeve having a through hole formed therein lengthwise of said barrel members and having a tapered abutment formed in said hole;
  • a depressible push button slidably fitted to the upper end ofsaid upper barrel member
  • a lengthwise movable needle member disposed in said guide member and engageable with the upper end of said pencil lead in the cartridge to limit the upward motion of said pencil lead;
  • a stop member fixed to the upper end of said needle member and having a diameter larger than that of the through hole of the sleeve;
  • a chuck connected at its stock portion with the lower end of said guide tube and provided with jaws equally arranged in the peripheral direction, each jaw having a shoulder engageable with said abutment of the chuck sleeve to close said chuck for holding said needle member and allowing the cartridge to project from the tip upon depression of said push button;
  • a compression spring surrounding said guide tube and disposed between said chuck sleeve and-said push button to urge said chuck upward.
  • a mechanical pencil comprising:
  • tubular cartridge slidably and coaxially inserted into said tip and the lower portion of said barrel and having a piece of pencil lead coaxially passing therethrough;
  • an elastic ring shaped brake member disposed in the lower part of said barrel to frictionally engage and hold said cartridge when it is inserted thereinto;
  • a depressible push button slidably fitted to the upper end of said barrel
  • a lengthwise movable needle member disposed in said guide member and engageable with the upper end of said pencil lead in the cartridge to limit the upward motion of said pencil lead;
  • a stop member fixed to the upper end of said needle member and having a diameter larger than that of the through hole of the sleeve;
  • a chuck connected at its stock tube with the lower end of said guide tube to move lower than the movable extent of of the chuck sleeve and provided with jaws equally arranged in the peripheral direction, each jaw having a shoulder engageable with said abutment of the chuck sleeve to close said chuck for holding said needle member and allowing the cartridge to project from the tip upon depression of said push button;
  • a compression spring surrounding said guide tube and disposed in the upper portion of said barrel to urge said chuck upward.
  • a mechanical pencil comprising:
  • a second barrel member which includes a first cylindrical portion, a second cylindrical portion of transparent resin material having one end connected to one end of said first cylindrical portion, said second cylindrical portion having a coaxial through hole therein, and a third cylindrical portion one end of which is connected to the other end of said second cylindrical portion and the other end of which is connected to one end of said first barrel member;
  • a brake member disposed in said first barrel member so as to frictionally engage and hold said cartridge
  • a guide tube disposed in said first cylindrical portion of said second barrel member and having one end inserted into said through hole in the second cylin drical portion of said second barrel member;
  • a chuck disposed in said third cylindrical portion and having one end fixed to the other end of said guide tube;
  • a sleeve located in said third cylindrical portion of said second barrel member, both ends of said sleeve being engageable with said other end of the second cylindrical portion of the second barrel memberand the chuck respectively; a lengthwise movable needle member coaxially disposed in said guide tube and penetrating through said chuck so as to be engageable with that end of said lead pencil which faces the first cylindrical portion of said second barrel member for prevention of the movement of said pencil lead toward said first cylindrical portion;
  • the mechanical pencil according to claim 11 further comprising a ring guide member in the abutment member, said ring guide member having a through hole therein to guide the needle member for alignment with the pencil lead in the cartridge.
  • a mechanical pencil comprising:
  • a lengthwise movable needle member coaxially disposed in said barrel and engageable at the lower end thereof with the upper end of said pencil lead to prevent the upward movement of said lead;
  • depressible means slidably mounted at the upper end of said barrel
  • chucking means formed substantially integral with said depressible means to normally hold in position said needle member which penetrates through said chucking means and causes the cartridge to project from the lower end of the barrel upon depression of said depressible means;
  • a sleeve located in said barrel to normally close said chucking means and having a through hole therein through which said needle member'passes, said sleeve being disengaged from said chucking means to open said chucking means upon depression of said depressible means;
  • said needle member being provided with a stop member having a larger diameter than that of the through hole of said sleeve;
  • urging means disposed between said sleeve and depressible means to urge said chucking means upward.

Landscapes

  • Mechanical Pencils And Projecting And Retracting Systems Therefor, And Multi-System Writing Instruments (AREA)
US00164271A 1971-05-11 1971-07-20 Mechanical pencil Expired - Lifetime US3729267A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP1971037591U JPS5113147Y2 (enrdf_load_stackoverflow) 1971-05-11 1971-05-11

Publications (1)

Publication Number Publication Date
US3729267A true US3729267A (en) 1973-04-24

Family

ID=12501771

Family Applications (1)

Application Number Title Priority Date Filing Date
US00164271A Expired - Lifetime US3729267A (en) 1971-05-11 1971-07-20 Mechanical pencil

Country Status (3)

Country Link
US (1) US3729267A (enrdf_load_stackoverflow)
JP (1) JPS5113147Y2 (enrdf_load_stackoverflow)
BE (1) BE778234A (enrdf_load_stackoverflow)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
USD272423S (en) 1981-02-05 1984-01-31 Nils-Eric Anderberg Aircraft docking display

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5333707U (enrdf_load_stackoverflow) * 1976-08-31 1978-03-24

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE338597C (de) * 1920-02-27 1921-06-21 Paul Lucas Bleistifthalter mit verschiebbarer Mine
US3537799A (en) * 1967-12-20 1970-11-03 Fumiko Sakamoto Mechanical pencil
US3627434A (en) * 1969-05-14 1971-12-14 Dainihon Bungu Co Ltd Mechanical pencil for fine leads

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5140613Y2 (enrdf_load_stackoverflow) * 1973-05-31 1976-10-04

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE338597C (de) * 1920-02-27 1921-06-21 Paul Lucas Bleistifthalter mit verschiebbarer Mine
US3537799A (en) * 1967-12-20 1970-11-03 Fumiko Sakamoto Mechanical pencil
US3627434A (en) * 1969-05-14 1971-12-14 Dainihon Bungu Co Ltd Mechanical pencil for fine leads

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
USD272423S (en) 1981-02-05 1984-01-31 Nils-Eric Anderberg Aircraft docking display

Also Published As

Publication number Publication date
JPS5113147Y2 (enrdf_load_stackoverflow) 1976-04-08
BE778234A (fr) 1972-05-16
JPS4736531U (enrdf_load_stackoverflow) 1972-12-22

Similar Documents

Publication Publication Date Title
US4180339A (en) Mechanical pencil with automatic lead feed
US4358210A (en) Mechanical pencil with chuck closing by normal writing grip
US3947133A (en) Automatic pencil
US7207738B2 (en) Writing instrument
US5988913A (en) Double-chuck mechanical pencil
US6749354B2 (en) Composite writing implement
US4148591A (en) Writing unit locking mechanism in a multiple-point writing implement including a mechanical pencil unit
US3729267A (en) Mechanical pencil
US4218153A (en) Mechanical pencil
GB2090202A (en) Propelling pencil having a replaceable square-lead holder
US4729684A (en) Mechanical pencil
US1969085A (en) Automatic lead pencil
EP0709233A1 (en) Slider for mechanical pencil
US2563551A (en) Pencil
US4165941A (en) Mechanical pencil
US2700959A (en) Mechanical pencil
EP0213275B1 (en) Automatic mechanical pencil
US3051131A (en) Retractable ball-point pen
US3442596A (en) Mechanical pencil of the push-out type
US1846604A (en) Magazine pencil
GB854118A (en) Protraction-retraction mechanism for writing instruments
JP2020104414A (ja) 芯繰出具
US2503080A (en) Mechanical pencil with push-button type lead feeding means
KR930003576Y1 (ko) 플로터용 샤아프펜슬
JPH0344549Y2 (enrdf_load_stackoverflow)