US2352813A - Magazine safety razor - Google Patents

Magazine safety razor Download PDF

Info

Publication number
US2352813A
US2352813A US513346A US51334643A US2352813A US 2352813 A US2352813 A US 2352813A US 513346 A US513346 A US 513346A US 51334643 A US51334643 A US 51334643A US 2352813 A US2352813 A US 2352813A
Authority
US
United States
Prior art keywords
magazine
blade
slot
blades
safety razor
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
US513346A
Inventor
Testi Nicholas
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.)
Gillette Co LLC
Original Assignee
Gillette Safety Razor Co
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 Gillette Safety Razor Co filed Critical Gillette Safety Razor Co
Priority to US513346A priority Critical patent/US2352813A/en
Application granted granted Critical
Publication of US2352813A publication Critical patent/US2352813A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • BPERFORMING OPERATIONS; TRANSPORTING
    • B26HAND CUTTING TOOLS; CUTTING; SEVERING
    • B26BHAND-HELD CUTTING TOOLS NOT OTHERWISE PROVIDED FOR
    • B26B21/00Razors of the open or knife type; Safety razors or other shaving implements of the planing type; Hair-trimming devices involving a razor-blade; Equipment therefor
    • B26B21/08Razors of the open or knife type; Safety razors or other shaving implements of the planing type; Hair-trimming devices involving a razor-blade; Equipment therefor involving changeable blades
    • B26B21/14Safety razors with one or more blades arranged transversely to the handle
    • B26B21/24Safety razors with one or more blades arranged transversely to the handle of the magazine type; of the injector type

Definitions

  • This invention relates to safety razors and consists in a new and improved safety razor of the magazine type in which a substantial number of fresh unused .blades are maintained in readily conveniently bring a sharp blade into operation at any time preparatory to or during a, shaving operation.
  • the invention includes within its scope a novel magazine which may serve as a dispensing receptacle for blades. Such a magazine'may be.
  • the principal object of the present invention is to insure positively against any im- 3 pairment of the blade edge from such causes by insuring complete protection of the blade from fully protected position to its slot in the magazine to its shaving position.above the guard.
  • a clamping screw projects forwardly from the back of the safety razor and into the magazine .where it may engage the rear edge of whichever blade is to be presented in shaving position.
  • This arrangement is made possible by perforating each blade and arranging th blades in the magazine so that the perforation in one blade provides clearance .of the clamping screw in engaging and advancing the particular blade selected for shaving.
  • the magazine may have any desired number of faces but is shown herein as having four faces and as containing four blades. This arrangement brings the blade slots and the contained blades into right angular relation, but it will be apparent that equivalent results could be secured in a magazine of hexagonal, octagonal or even cylindrical cross-section.
  • the razor includes an open channel in which the magazine may be readily inserted and from which it may be temporarily removed when it is desired to bring a fresh bladejnto operative position or to reload the magazine with a charge 'of fresh blades. In this connection one the time it leaves the'manufacturers hands to the time it is moved the least fraction into its final shaving position.
  • an important feature of the invention consists in a safety razor having an open channel and a guard, in combina-.
  • a magazine filling the channel and having a plurality of internal blade-receiving slots which open out through a portion of the magazine so located that'the' blade may be an vanced from a protected position directly out of the slot and into shaving position with respect to the guard; all without the possibility of any contact with the keen sharp edge'of the blade.
  • the blade-receiving slots are arranged tangent to a common circle and each leads to one comer edge of the magazine. Slots arranged in this way provide convenient and compact distributionof blades in a magazine.
  • Another fe'ature'of the invention consists in a provision of convenient and easily accessible of an inch means for advancing any selected blade from 66 wall of the channel may be made resilient for the purpose of yieldingly retaining the magazine in the safety razor while permitting its removal at any time.
  • Fig. 1 is a view in perspective of the complete razor on'an enlarged scale:
  • Fig. 2 is a similar view of from a different angle
  • Fig. 3 is a view in perspective showing the parts of the razorhead, the magazine of the blades in exploded relation;
  • Fig. 4 is a view of the razorhead in cross-sec- .tion on a scale still more enlarged and Fig. 5 is a similar view showing one of the blades advanced into shaving position.
  • the razor comprises a handle I 0 carrying at its upper end a head presenting a transversely disposed open channel which is substantially square in cross-section.
  • a thin resilient back plate il carrying at its upper end a head presenting a transversely disposed open channel which is substantially square in cross-section.
  • the back plate I I has a rectangular body and a downwardly prothe razor head seen jecting shank portion which is clamped to a fiat- 'tened rear face of the handleby screws l3 pass ing also through the clamping bar l2.
  • the clamping bar is a straight stifl bar l2 overlying the downwardly projecting shank portion of the back plate H, thickened substantially at its upper end and extending to within a short distance of the upper edge of the back plate H.
  • the thickened upper end of the clamping bar is drilled and tapped to receive a blade-locating and clamping screw l1 having an enlarged knurled head by which it may be conveniently turned by ingposition, as shown in Fig. 5,- its perforation between them is a guard bar It having projecting blade stop lugs ill at each end and a curved skin-engaging face.
  • the blade magazine herein shown comprises an elongated rectangular block 20 shaped to fit into the channel of the razor head so that it may be readily presented thereto by pushing it vertically into the channel or by pushing it in endwise.
  • the block 20 maybe of wood or plastic material orlight metal and is preferably bored longitudinally for the sake of lightness. It is provided with four blade slots 2
  • the arrangement is such that the slots lie tangentto a circle which is common to all of them'and described on the axis of the magazine block as a center.
  • Each slot is disposed at right angles to the next adjacent slot and deep enough completely to receive and protect a blade therein.
  • the magazine block is of such size and shape that the plane of the slot 2
  • a bore22 Leading from theinner edge of each blade slot 2
  • the screw I! normally extends into one of the bores 22 of the magazine block and so retains the magazine in the razor head; when it is desired to release the magazine the screw I'Lmay be backed out sufliciently to disengage it, whereupon the magazine may be lifted out of its channel and turned to bring a fresh blade into operative position or may be reloaded with four fresh blades.
  • the screw 11 On the other handswhen it is desired to advance a blade into shaving position the screw 11 is turned inwardly engaging the rear edge of one of the blades 23 and advancing it'out of its slot until the blade is arrested by engaging the two blade stops I8 at its opposite comers. When the screw I1 is advanced it positively supports the selected blade in shaving position.
  • the magazine herein illustrated is shown as adaptedto handle-and present thin straight single-edged blades 23 as shown in Fig. 3.
  • Each of these blades is provided with a perforation 24 midway between its ends and slightly nearer to its sharpened edge than to its rear edge.
  • the purpose of the perforation 24 is to afford 01684- 24 is carried forwardly and the bore 22 substantially closed.
  • the blade 23 which is uppermost in the magazine and which is disposed substantially horizontally is brought into registration with the screw l1 and the latter passes through the perforation 24 of the blade which happens to be located rearwardly and substantially. ver-. tically in the magazine.
  • Each face of the magazine is numbered to enable the user to keep track of the blades used by him; that is, he may start a fresh magazine with its No. 1 face uppermost and then progress to the subsequently numbered faces.
  • the upper edge of the back plate II is slightly flared so that the plate may be sprung rearwardly in admitting the magazine while it yieldingly holds the magazine in place when the latter has been inserted in the channel of the head.
  • the magazine block may be conveniently loaded by the manufacturer, the newly ground, stropped and honed blades being inserted by mechanical means without danger'to their sharp edges. If desired they may have a light coating of grease and this tends to holdthe blades in place in their respective slots and also to protect them from rusting.
  • the loaded magazine block may be wrapped and handled as a, unit of merchandise in distribution and sale.
  • a magazine razor having a holder, a removable magazine block therein having a series of longitudinal slots, each disposed at right angles to the next adjacent slot, a perforated blade in each slot, and a screw threaded into the holder, passing through the-perforation in one blade and abutting the rear edge of the blade in the adjacent slot.
  • a magazine razor having a holder, a magazine substantially square in cross section, fitting in said holder and having a series of slots each opening out through one corner edge of the block and extending inwardly at an acute angle to the adjacent face of the magazine, a bore leading from each slot to the opposite face of the magazine, and a blade-clamping screw projecting into said bore from the holder.
  • a magazine safety razor having a holder with front and rear walls, the front wall carrying a guard, and a retaining screw arranged to be projected forwardly from the rear wall, in combination with a magazine fitting between said walls, having a blade-retaining slot leading toward the guard and a transverse bore for receiving the retaining screw.
  • a safety razor having a holder of rectangular cross-section opening upwardly, a guard at one side of said opening, and a blade-clamping screw at the other, in combination with a magazine of rectangular cross-section having an internal blade slot disposed adjacent to and making an angle with that face of the magazine which is uppermost in the holder and a bore in the magazine providing access by the clamping screw to the rear edge of a blade contained in said slot.
  • a safety razor having magazine-retaining walls, a guard, and a transverse blade-positioning screw projecting inwardly at a predetermined height from one of said walls, in combination with an elongated magazine of symmetrical shape fit ting between said walls and having a series of blade-containing slots so disposed that by rotating the magazine any selected slot may be brought into registration with said screw.
  • a magazine safety razor including in its structure guarding means and blade-advancing means, in combination with a cooperating magazine symmetrical in cross-section and having a series of internal blade-receiving slots disposed at diflerent angles and so located that in all positions of the magazine one slot is disposed in alignment with both the guarding means and the blade-advancing means.
  • a magazine safety razor having a holder presenting an open recess, a magazine filling the recess of the holder and provided with a plurality of blade-receiving slots opening through peripheral surfaces of the magazine, a blade of uniform thickness wholly concealed within each slot and movable therein, and means in the holder constructed and arranged to enter the magazine, advance any selected blade outwardly in its slot and positively hold the selected blade in shaving position.

Description

July 4, 1944. N EST 2,352,813
v MAGAZINE SAFETY RAZOR Filed Dec. 8, 1943 accessible position so that the user may Patented July 4, 1944 MAGAZINE SAFETYRAZOR Nicholas 'lesti, Boston, Mass., assignor to Gil-- lette Safety Razor Co mnany. Boston. Mass., a
corporation of Delaware Application December a, 1943, Serial no. 513,346
' This invention relates to safety razors and consists in a new and improved safety razor of the magazine type in which a substantial number of fresh unused .blades are maintained in readily conveniently bring a sharp blade into operation at any time preparatory to or during a, shaving operation. The invention includes within its scope a novel magazine which may serve as a dispensing receptacle for blades. Such a magazine'may be.
loaded by the manufacturer with the desired number of blades and these are then effectively protected against damage to the fragile structure of their keen sharp edges and maintained in this fully protected condition until the magazine is placed in the safety razor and the blade actually advanced directly into shaving position.
In handling safety razor blades under/commercial conditions of transportation and distribution and in the more or less casual treatment to which such blades are subjected by the user the extremely fine keen edge of the blade is likely to become dulled by being brought intov contact with its wrapping or with other objects before it can beactually clamped in shaving position in the razor. On this account'the best and most skillful eflorts of the manufacturer in sharpening the blades are often brought to naught. The principal object of the present invention is to insure positively against any im- 3 pairment of the blade edge from such causes by insuring complete protection of the blade from fully protected position to its slot in the magazine to its shaving position.above the guard. As herein shown a clamping screw projects forwardly from the back of the safety razor and into the magazine .where it may engage the rear edge of whichever blade is to be presented in shaving position. This arrangement is made possible by perforating each blade and arranging th blades in the magazine so that the perforation in one blade provides clearance .of the clamping screw in engaging and advancing the particular blade selected for shaving.
The magazine may have any desired number of faces but is shown herein as having four faces and as containing four blades. This arrangement brings the blade slots and the contained blades into right angular relation, but it will be apparent that equivalent results could be secured in a magazine of hexagonal, octagonal or even cylindrical cross-section. Preferably and as herein shown the razor includes an open channel in which the magazine may be readily inserted and from which it may be temporarily removed when it is desired to bring a fresh bladejnto operative position or to reload the magazine with a charge 'of fresh blades. In this connection one the time it leaves the'manufacturers hands to the time it is moved the least fraction into its final shaving position.
With these objects in view an important feature of the invention consists in a safety razor having an open channel and a guard, in combina-.
tion with. a magazine filling the channel and having a plurality of internal blade-receiving slots which open out through a portion of the magazine so located that'the' blade may be an vanced from a protected position directly out of the slot and into shaving position with respect to the guard; all without the possibility of any contact with the keen sharp edge'of the blade. Preferably and as herein shown the blade-receiving slots are arranged tangent to a common circle and each leads to one comer edge of the magazine. Slots arranged in this way provide convenient and compact distributionof blades in a magazine.
Another fe'ature'of the invention consists in a provision of convenient and easily accessible of an inch means for advancing any selected blade from 66 wall of the channel may be made resilient for the purpose of yieldingly retaining the magazine in the safety razor while permitting its removal at any time.
. These and other features of the invention will be best understood and appreciated from the following description of a preferred embodiment thereof selected for purposes of illustration and shown in the accompanying drawing, in which:
Fig. 1 is a view in perspective of the complete razor on'an enlarged scale:
Fig. 2 is a similar view of from a different angle;
Fig. 3 is a view in perspective showing the parts of the razorhead, the magazine of the blades in exploded relation;
Fig. 4 is a view of the razorhead in cross-sec- .tion on a scale still more enlarged and Fig. 5 is a similar view showing one of the blades advanced into shaving position.
.The razor comprises a handle I 0 carrying at its upper end a head presenting a transversely disposed open channel which is substantially square in cross-section. In the razorhead are included a thin resilient back plate il, a clamping bar 12 and a guard member. The back plate I I has a rectangular body and a downwardly prothe razor head seen jecting shank portion which is clamped to a fiat- 'tened rear face of the handleby screws l3 pass ing also through the clamping bar l2. The clamping bar is a straight stifl bar l2 overlying the downwardly projecting shank portion of the back plate H, thickened substantially at its upper end and extending to within a short distance of the upper edge of the back plate H. The thickened upper end of the clamping bar is drilled and tapped to receive a blade-locating and clamping screw l1 having an enlarged knurled head by which it may be conveniently turned by ingposition, as shown in Fig. 5,- its perforation between them is a guard bar It having projecting blade stop lugs ill at each end and a curved skin-engaging face.
The blade magazine herein shown comprises an elongated rectangular block 20 shaped to fit into the channel of the razor head so that it may be readily presented thereto by pushing it vertically into the channel or by pushing it in endwise. The block 20 maybe of wood or plastic material orlight metal and is preferably bored longitudinally for the sake of lightness. It is provided with four blade slots 2|, each slot opening out through one of the corner edges of the block '20 and extending inwardly at an angle of about 20 to the face of the block immediately above it. The arrangement is such that the slots lie tangentto a circle which is common to all of them'and described on the axis of the magazine block as a center. Each slot is disposed at right angles to the next adjacent slot and deep enough completely to receive and protect a blade therein.
The magazine block is of such size and shape that the plane of the slot 2| which is uppermost is substantially tangent to the surface of the guard bar l6 and positions a blade properly to be advanced out of the slot and across the guard bar until arrested by the blade stops l8. Leading from theinner edge of each blade slot 2| in the magazine block is a bore22 which opens through the wall of the magazine opposite the opening of the blade slot and in alignment with the screw ll.
The screw I! normally extends into one of the bores 22 of the magazine block and so retains the magazine in the razor head; when it is desired to release the magazine the screw I'Lmay be backed out sufliciently to disengage it, whereupon the magazine may be lifted out of its channel and turned to bring a fresh blade into operative position or may be reloaded with four fresh blades. On the other handswhen it is desired to advance a blade into shaving position the screw 11 is turned inwardly engaging the rear edge of one of the blades 23 and advancing it'out of its slot until the blade is arrested by engaging the two blade stops I8 at its opposite comers. When the screw I1 is advanced it positively supports the selected blade in shaving position.
The magazine herein illustrated is shown as adaptedto handle-and present thin straight single-edged blades 23 as shown in Fig. 3. Each of these blades is provided with a perforation 24 midway between its ends and slightly nearer to its sharpened edge than to its rear edge. The purpose of the perforation 24 is to afford 01684- 24 is carried forwardly and the bore 22 substantially closed. The blade 23 which is uppermost in the magazine and which is disposed substantially horizontally is brought into registration with the screw l1 and the latter passes through the perforation 24 of the blade which happens to be located rearwardly and substantially. ver-. tically in the magazine. Each face of the magazine is numbered to enable the user to keep track of the blades used by him; that is, he may start a fresh magazine with its No. 1 face uppermost and then progress to the subsequently numbered faces.
The upper edge of the back plate II is slightly flared so that the plate may be sprung rearwardly in admitting the magazine while it yieldingly holds the magazine in place when the latter has been inserted in the channel of the head.
The magazine block may be conveniently loaded by the manufacturer, the newly ground, stropped and honed blades being inserted by mechanical means without danger'to their sharp edges. If desired they may have a light coating of grease and this tends to holdthe blades in place in their respective slots and also to protect them from rusting. The loaded magazine block may be wrapped and handled as a, unit of merchandise in distribution and sale.
Having thus disclosed my invention and described in detail an illustrative embodiment there f I claim as new and desire to secure by ing an open channel having a front wall with a guard bar and an opposed rear wall, a magazine fitting between said front and rear walls and having an internal slot opening adjacent to the said guard bar, and a screw movable through the rear vgall of the holder for advancing a blade in its s ot.
3. A magazine razor having a holder, a removable magazine block therein having a series of longitudinal slots, each disposed at right angles to the next adjacent slot, a perforated blade in each slot, and a screw threaded into the holder, passing through the-perforation in one blade and abutting the rear edge of the blade in the adjacent slot.
, 4. .A magazine razor having a holder, a magazine substantially square in cross section, fitting in said holder and having a series of slots each opening out through one corner edge of the block and extending inwardly at an acute angle to the adjacent face of the magazine, a bore leading from each slot to the opposite face of the magazine, and a blade-clamping screw projecting into said bore from the holder.
5. A magazine safety razor having a holder with front and rear walls, the front wall carrying a guard, and a retaining screw arranged to be projected forwardly from the rear wall, in combination with a magazine fitting between said walls, having a blade-retaining slot leading toward the guard and a transverse bore for receiving the retaining screw.
6. A safety razor having a holder of rectangular cross-section opening upwardly, a guard at one side of said opening, and a blade-clamping screw at the other, in combination with a magazine of rectangular cross-section having an internal blade slot disposed adjacent to and making an angle with that face of the magazine which is uppermost in the holder and a bore in the magazine providing access by the clamping screw to the rear edge of a blade contained in said slot.
7. A safety razor having magazine-retaining walls, a guard, and a transverse blade-positioning screw projecting inwardly at a predetermined height from one of said walls, in combination with an elongated magazine of symmetrical shape fit ting between said walls and having a series of blade-containing slots so disposed that by rotating the magazine any selected slot may be brought into registration with said screw.
8. A magazine safety razor including in its structure guarding means and blade-advancing means, in combination with a cooperating magazine symmetrical in cross-section and having a series of internal blade-receiving slots disposed at diflerent angles and so located that in all positions of the magazine one slot is disposed in alignment with both the guarding means and the blade-advancing means.
9. A magazine safety razor having a holder presenting an open recess, a magazine filling the recess of the holder and provided with a plurality of blade-receiving slots opening through peripheral surfaces of the magazine, a blade of uniform thickness wholly concealed within each slot and movable therein, and means in the holder constructed and arranged to enter the magazine, advance any selected blade outwardly in its slot and positively hold the selected blade in shaving position. I
NICHOLAS TESTI.
US513346A 1943-12-08 1943-12-08 Magazine safety razor Expired - Lifetime US2352813A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
US513346A US2352813A (en) 1943-12-08 1943-12-08 Magazine safety razor

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US513346A US2352813A (en) 1943-12-08 1943-12-08 Magazine safety razor

Publications (1)

Publication Number Publication Date
US2352813A true US2352813A (en) 1944-07-04

Family

ID=24042871

Family Applications (1)

Application Number Title Priority Date Filing Date
US513346A Expired - Lifetime US2352813A (en) 1943-12-08 1943-12-08 Magazine safety razor

Country Status (1)

Country Link
US (1) US2352813A (en)

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2565062A (en) * 1949-11-14 1951-08-21 Hyman A Blanchard Razor
DE1728528A1 (en) * 1965-04-29 1974-05-30 Wilkinson Sword Ltd DISPENSER FOR RAZOR BLADES AND ASSOCIATED RAZOR
US4916814A (en) * 1987-01-03 1990-04-17 Wilkinson Sword Gesellschaft Mit Beschrankter Haftung Wet-shave razor
US5595424A (en) * 1994-04-27 1997-01-21 S.T. Japan Inc. Mini plane
USD388540S (en) * 1996-12-04 1997-12-30 Haim Ramar Razor having a rotatable triangular head
US20110173821A1 (en) * 2010-01-21 2011-07-21 Preston Hage, Llc Safety razor
USD829993S1 (en) 2017-08-15 2018-10-02 Preston Hage, Llc Handle for a safety razor
USD829992S1 (en) 2017-01-30 2018-10-02 Preston Hage, Llc Cartridge head for a safety razor
USD830632S1 (en) 2017-01-30 2018-10-09 Preston Hage, Llc Safety razor
USD850723S1 (en) 2018-01-09 2019-06-04 Preston Hage, Llc Safety razor chassis
US10882200B1 (en) * 2018-12-12 2021-01-05 Mark Shabel Razor with rotatable blade head

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2565062A (en) * 1949-11-14 1951-08-21 Hyman A Blanchard Razor
DE1728528A1 (en) * 1965-04-29 1974-05-30 Wilkinson Sword Ltd DISPENSER FOR RAZOR BLADES AND ASSOCIATED RAZOR
US4916814A (en) * 1987-01-03 1990-04-17 Wilkinson Sword Gesellschaft Mit Beschrankter Haftung Wet-shave razor
US5595424A (en) * 1994-04-27 1997-01-21 S.T. Japan Inc. Mini plane
USD388540S (en) * 1996-12-04 1997-12-30 Haim Ramar Razor having a rotatable triangular head
US20110173821A1 (en) * 2010-01-21 2011-07-21 Preston Hage, Llc Safety razor
US8745876B2 (en) * 2010-01-21 2014-06-10 Preston Hage, Llc Safety razor
USD829992S1 (en) 2017-01-30 2018-10-02 Preston Hage, Llc Cartridge head for a safety razor
USD830632S1 (en) 2017-01-30 2018-10-09 Preston Hage, Llc Safety razor
USD829993S1 (en) 2017-08-15 2018-10-02 Preston Hage, Llc Handle for a safety razor
USD850723S1 (en) 2018-01-09 2019-06-04 Preston Hage, Llc Safety razor chassis
US10882200B1 (en) * 2018-12-12 2021-01-05 Mark Shabel Razor with rotatable blade head

Similar Documents

Publication Publication Date Title
US2352813A (en) Magazine safety razor
US2472051A (en) Blade-dispensing container
US2311913A (en) Safety razor and protected blade
US2352113A (en) Safety razor magazine
US2744317A (en) Safety razor and blade changer therefor
US1588322A (en) Razor-blade sharpener
US2270790A (en) Magazine for safety razor blades
US2418677A (en) Razor blade dispensing container
US1490458A (en) Safety razor
US2312502A (en) Blade magazine
US2392433A (en) Magazine for safety razor blades
US956532A (en) Safety-razor.
US2350837A (en) Magazine for safety razor blades
US2312453A (en) Magazine for safety razor blades
US3377703A (en) Razor blade holder
US2342161A (en) Safety razor
US2601601A (en) Razor blade injector and disposal device
US2731715A (en) Paper carton cutter
US2348303A (en) Magazine for safety razor blades
US4047295A (en) Shaving unit dispenser container
US2342160A (en) Safety razor
US2424593A (en) Safety razor blade and magazine therefor
US2534666A (en) Corn knife
US2363608A (en) Safety razor
US2356188A (en) Safety razor